[ARM] Cleanup arch/arm/mm a little

Move top_pmd into arch/arm/mm/mm.h - nothing outside arch/arm/mm
references it.

Move the repeated definition of TOP_PTE into mm/mm.h, as well as
a few function prototypes.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mm/flush.c

@@ -15,12 +15,12 @@
 #include <asm/system.h>
 #include <asm/tlbflush.h>
 
+#include "mm.h"
+
 #ifdef CONFIG_CPU_CACHE_VIPT
 
 #define ALIAS_FLUSH_START	0xffff4000
 
-#define TOP_PTE(x)	pte_offset_kernel(top_pmd, x)
-
 static void flush_pfn_alias(unsigned long pfn, unsigned long vaddr)
 {
 	unsigned long to = ALIAS_FLUSH_START + (CACHE_COLOUR(vaddr) << PAGE_SHIFT);