powerpc: tlb_32.c build fix

allnoconfig results in this:

 CC      arch/powerpc/mm/tlb_32.o
In file included from include/asm/tlb.h:60,
                 from arch/powerpc/mm/tlb_32.c:30:
include/asm-generic/tlb.h: In function 'tlb_flush_mmu':
include/asm-generic/tlb.h:76: error: implicit declaration of function 'release_pages'
include/asm-generic/tlb.h: In function 'tlb_remove_page':
include/asm-generic/tlb.h:105: error: implicit declaration of function 'page_cache_release'

Signed-off-by: Mariusz Kozlowski <m.kozlowski@tuxland.pl>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/powerpc/mm/tlb_32.c

@@ -26,6 +26,8 @@
 #include <linux/mm.h>
 #include <linux/init.h>
 #include <linux/highmem.h>
+#include <linux/pagemap.h>
+
 #include <asm/tlbflush.h>
 #include <asm/tlb.h>