ACPI: Clean up acpi_os_map/unmap_memory() to eliminate __iomem.

ACPICA doesn't include protections around address space checking, Linux
build tests always complain increased sparse warnings around ACPICA
internal acpi_os_map/unmap_memory() invocations.  This patch tries to fix
this issue permanently.

There are 2 choices left for us to solve this issue:
 1. Add __iomem address space awareness into ACPICA.
 2. Remove sparse checker of __iomem from ACPICA source code.

This patch chooses solution 2, because:
 1.  Most of the acpi_os_map/unmap_memory() invocations are used for ACPICA.
     table mappings, which in fact are not IO addresses.
 2.  The only IO addresses usage is for "system memory space" mapping code in:
      drivers/acpi/acpica/exregion.c
      drivers/acpi/acpica/evrgnini.c
      drivers/acpi/acpica/exregion.c
    The mapped address is accessed in the handler of "system memory space"
    - acpi_ex_system_memory_space_handler().  This function in fact can be
    changed to invoke acpi_os_read/write_memory() so that __iomem can
    always be type-casted in the OSL layer.

According to the above investigation, we drew the following conclusion:
It is not a good idea to introduce __iomem address space awareness into
ACPICA mostly in order to protect non-IO addresses.

We can simply remove __iomem for acpi_os_map/unmap_memory() to remove
__iomem checker for ACPICA code. Then we need to enforce external usages
to invoke other APIs that are aware of __iomem address space.
The external usages are:
 drivers/acpi/apei/einj.c
 drivers/acpi/acpi_extlog.c
 drivers/char/tpm/tpm_acpi.c
 drivers/acpi/nvs.c

This patch thus performs cleanups in this way:
 1. Add acpi_os_map/unmap_iomem() to be invoked by non-ACPICA code.
 2. Remove __iomem from acpi_os_map/unmap_memory().

Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/osl.c

@@ -355,7 +355,7 @@ static void acpi_unmap(acpi_physical_address pg_off, void __iomem *vaddr)
 }
 
 void __iomem *__init_refok
-acpi_os_map_memory(acpi_physical_address phys, acpi_size size)
+acpi_os_map_iomem(acpi_physical_address phys, acpi_size size)
 {
 	struct acpi_ioremap *map;
 	void __iomem *virt;
@@ -401,10 +401,17 @@ acpi_os_map_memory(acpi_physical_address phys, acpi_size size)
 
 	list_add_tail_rcu(&map->list, &acpi_ioremaps);
 
- out:
+out:
 	mutex_unlock(&acpi_ioremap_lock);
 	return map->virt + (phys - map->phys);
 }
+EXPORT_SYMBOL_GPL(acpi_os_map_iomem);
+
+void *__init_refok
+acpi_os_map_memory(acpi_physical_address phys, acpi_size size)
+{
+	return (void *)acpi_os_map_iomem(phys, size);
+}
 EXPORT_SYMBOL_GPL(acpi_os_map_memory);
 
 static void acpi_os_drop_map_ref(struct acpi_ioremap *map)
@@ -422,7 +429,7 @@ static void acpi_os_map_cleanup(struct acpi_ioremap *map)
 	}
 }
 
-void __ref acpi_os_unmap_memory(void __iomem *virt, acpi_size size)
+void __ref acpi_os_unmap_iomem(void __iomem *virt, acpi_size size)
 {
 	struct acpi_ioremap *map;
 
@@ -443,6 +450,12 @@ void __ref acpi_os_unmap_memory(void __iomem *virt, acpi_size size)
 
 	acpi_os_map_cleanup(map);
 }
+EXPORT_SYMBOL_GPL(acpi_os_unmap_iomem);
+
+void __ref acpi_os_unmap_memory(void *virt, acpi_size size)
+{
+	return acpi_os_unmap_iomem((void __iomem *)virt, size);
+}
 EXPORT_SYMBOL_GPL(acpi_os_unmap_memory);
 
 void __init early_acpi_os_unmap_memory(void __iomem *virt, acpi_size size)
@@ -464,7 +477,7 @@ int acpi_os_map_generic_address(struct acpi_generic_address *gas)
 	if (!addr || !gas->bit_width)
 		return -EINVAL;
 
-	virt = acpi_os_map_memory(addr, gas->bit_width / 8);
+	virt = acpi_os_map_iomem(addr, gas->bit_width / 8);
 	if (!virt)
 		return -EIO;