powerpc: Fix bug arising from having multiple memory_limit variables

We had a static memory_limit in prom.c, and then another one defined
in setup_64.c and used in numa.c, which resulted in the kernel crashing
when mem=xxx was given on the command line.  This puts the declaration
in system.h and the definition in mem.c.  This also moves the
definition of tce_alloc_start/end out of setup_64.c.

Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
index 6309a1a..2eccd0e 100644
--- a/arch/powerpc/kernel/prom.c
+++ b/arch/powerpc/kernel/prom.c
@@ -78,15 +78,13 @@
 extern struct lmb lmb;
 extern unsigned long klimit;
 
-static unsigned long memory_limit;
-
 static int __initdata dt_root_addr_cells;
 static int __initdata dt_root_size_cells;
 
 #ifdef CONFIG_PPC64
 static int __initdata iommu_is_off;
 int __initdata iommu_force_on;
-extern unsigned long tce_alloc_start, tce_alloc_end;
+unsigned long tce_alloc_start, tce_alloc_end;
 #endif
 
 typedef u32 cell_t;