sh/mm/pg-sh7705.c must #include <linux/fs.h>

This patch fixes the following compile error:

<--  snip  -->

...
  CC      arch/sh/mm/pg-sh7705.o
/home/bunk/linux/kernel-2.6/git/linux-2.6/arch/sh/mm/pg-sh7705.c: In function 'ptep_get_and_clear':
/home/bunk/linux/kernel-2.6/git/linux-2.6/arch/sh/mm/pg-sh7705.c:130: error: implicit declaration of function 'mapping_writably_mapped'
make[2]: *** [arch/sh/mm/pg-sh7705.o] Error 1

<--  snip  -->
Signed-off-by: NAdrian Bunk <adrian.bunk@movial.fi>
Signed-off-by: NPaul Mundt <lethal@linux-sh.org>

arch/sh/mm/pg-sh7705.c

@@ -14,6 +14,7 @@
 #include <linux/mman.h>
 #include <linux/mm.h>
 #include <linux/threads.h>
+#include <linux/fs.h>
 #include <asm/addrspace.h>
 #include <asm/page.h>
 #include <asm/pgtable.h>