[POWERPC] Rename __initial_memory_limit to __initial_memory_limit_addr

We always use __initial_memory_limit as an address so rename it
to be clear.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/mm/mmu_decl.h

@@ -48,7 +48,7 @@ extern unsigned int num_tlbcam_entries;
 
 extern unsigned long ioremap_bot;
 extern unsigned long __max_low_memory;
-extern unsigned long __initial_memory_limit;
+extern phys_addr_t __initial_memory_limit_addr;
 extern unsigned long total_memory;
 extern unsigned long total_lowmem;
 extern phys_addr_t memstart_addr;