m68k: __pa(): cast arg to long

Fixes this:

drivers/char/mem.c: In function 'mmap_kmem':
drivers/char/mem.c:342: warning: cast to pointer from integer of different size

by doing what other archtiectures do.

Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

arch/m68k/include/asm/page_mm.h

@@ -80,7 +80,7 @@ static inline unsigned long ___pa(void *vaddr)
 		: "0" (vaddr), "i" (m68k_fixup_memoffset));
 	return paddr;
 }
-#define __pa(vaddr)	___pa((void *)(vaddr))
+#define __pa(vaddr)	___pa((void *)(long)(vaddr))
 static inline void *__va(unsigned long paddr)
 {
 	void *vaddr;