[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>
diff --git a/arch/arm/mm/copypage-v6.c b/arch/arm/mm/copypage-v6.c
index 269ce69..3d0d3a9 100644
--- a/arch/arm/mm/copypage-v6.c
+++ b/arch/arm/mm/copypage-v6.c
@@ -17,6 +17,8 @@
 #include <asm/tlbflush.h>
 #include <asm/cacheflush.h>
 
+#include "mm.h"
+
 #if SHMLBA > 16384
 #error FIX ME
 #endif
@@ -24,8 +26,6 @@
 #define from_address	(0xffff8000)
 #define to_address	(0xffffc000)
 
-#define TOP_PTE(x)	pte_offset_kernel(top_pmd, x)
-
 static DEFINE_SPINLOCK(v6_lock);
 
 /*