powerpc: Merge lmb.c and make MM initialization use it.

This also creates merged versions of do_init_bootmem, paging_init
and mem_init and moves them to arch/powerpc/mm/mem.c.  It gets rid
of the mem_pieces stuff.

I made memory_limit a parameter to lmb_enforce_memory_limit rather
than a global referenced by that function.  This will require some
small changes to ppc64 if we want to continue building ARCH=ppc64
using the merged lmb.c.

Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/mm/Makefile

@@ -2,9 +2,9 @@
 # Makefile for the linux ppc-specific parts of the memory manager.
 #
 
-obj-y				:= fault.o mem.o
+obj-y				:= fault.o mem.o lmb.o
 obj-$(CONFIG_PPC32)		+= init.o pgtable.o mmu_context.o \
-				   mem_pieces.o tlb.o
+				   tlb.o
 obj-$(CONFIG_PPC64)		+= init64.o pgtable64.o mmu_context64.o
 obj-$(CONFIG_PPC_STD_MMU_32)	+= ppc_mmu.o hash_32.o
 obj-$(CONFIG_40x)		+= 4xx_mmu.o