mips: switch to NO_BOOTMEM

MIPS already has memblock support and all the memory is already registered
with it.

This patch replaces bootmem memory reservations with memblock ones and
removes the bootmem initialization.

Since memblock allocates memory in top-down mode, we ensure that memblock
limit is max_low_pfn to prevent allocations from the high memory.

To have the exceptions base in the lower 512M of the physical memory, its
allocation in arch/mips/kernel/traps.c::traps_init() is using bottom-up
mode.

Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Patchwork: https://patchwork.linux-mips.org/patch/20560/
Cc: Serge Semin <fancer.lancer@gmail.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: Huacai Chen <chenhc@lemote.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: linux-mips@linux-mips.org
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org

arch/mips/sgi-ip27/ip27-memory.c

@@ -389,7 +389,6 @@ static void __init node_mem_init(cnodeid_t node)
 {
 	unsigned long slot_firstpfn = slot_getbasepfn(node, 0);
 	unsigned long slot_freepfn = node_getfirstfree(node);
-	unsigned long bootmap_size;
 	unsigned long start_pfn, end_pfn;
 
 	get_pfn_range_for_nid(node, &start_pfn, &end_pfn);
@@ -400,7 +399,6 @@ static void __init node_mem_init(cnodeid_t node)
 	__node_data[node] = __va(slot_freepfn << PAGE_SHIFT);
 	memset(__node_data[node], 0, PAGE_SIZE);
 
-	NODE_DATA(node)->bdata = &bootmem_node_data[node];
 	NODE_DATA(node)->node_start_pfn = start_pfn;
 	NODE_DATA(node)->node_spanned_pages = end_pfn - start_pfn;
 
@@ -409,12 +407,11 @@ static void __init node_mem_init(cnodeid_t node)
 	slot_freepfn += PFN_UP(sizeof(struct pglist_data) +
 			       sizeof(struct hub_data));
 
-	bootmap_size = init_bootmem_node(NODE_DATA(node), slot_freepfn,
-					start_pfn, end_pfn);
 	free_bootmem_with_active_regions(node, end_pfn);
-	reserve_bootmem_node(NODE_DATA(node), slot_firstpfn << PAGE_SHIFT,
-		((slot_freepfn - slot_firstpfn) << PAGE_SHIFT) + bootmap_size,
-		BOOTMEM_DEFAULT);
+
+	memblock_reserve(slot_firstpfn << PAGE_SHIFT,
+			 ((slot_freepfn - slot_firstpfn) << PAGE_SHIFT));
+
 	sparse_memory_present_with_active_regions(node);
 }