ACPICA: Headers: Deploy #pragma pack (push) and (pop).

Use push and pop to both guarantee that the correct alignment is used,
and to restore the alignment to whatever it was before the header
was included.

It is reported that the #pragma pack(push/pop) directives are not supported
by the specific GCCs, but this patch still doesn't affect kernel build
as there are already #pragma pack([1]) directives used in the old ACPICA
headers, which means there shouldn't be GCCs that are currently used to
compile the ACPI kernels do not support #pragma pack() directives.

References: https://bugs.acpica.org/show_bug.cgi?id=1058
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/acpica/acpredef.h

@@ -44,6 +44,8 @@
 #ifndef __ACPREDEF_H__
 #define __ACPREDEF_H__
 
+#pragma pack(push)		/* Set default struct packing */
+
 /******************************************************************************
  *
  * Return Package types
@@ -1080,4 +1082,6 @@ static const union acpi_predefined_info acpi_gbl_scope_names[] = {
 extern const union acpi_predefined_info acpi_gbl_resource_names[];
 #endif
 
+#pragma pack(pop)		/* Restore original struct packing */
+
 #endif