CRIS v10: Include mm.h instead of vmstat.h in kernel/time.c

Commit 2f569afd
(CONFIG_HIGHPTE vs. sub-page page tables) introduced use of
inc_zone_page_state and dec_zone_page_state in include/linux/mm.h.

Those are defined in include/linux/vmstat.h, but after it includes
mm.h, making it impossible to include vmstat.h since inc_zone_page_state
and dec_zone_page_state then would be undefined.

arch/cris/arch-v10/kernel/time.c does just this, which makes the
CRIS v10 build break with the following error:

...
  CC      arch/cris/arch-v10/kernel/time.o
In file included from include/linux/vmstat.h:7,
                 from arch/cris/arch-v10/kernel/time.c:17:
include/linux/mm.h: In function 'pgtable_page_ctor':
include/linux/mm.h:902: error: implicit declaration of function 'inc_zone_page_state'
include/linux/mm.h: In function 'pgtable_page_dtor':
include/linux/mm.h:908: error: implicit declaration of function 'dec_zone_page_state'
make[2]: *** [arch/cris/arch-v10/kernel/time.o] Error 1
make[1]: *** [arch/cris/arch-v10/kernel] Error 2
make: *** [sub-make] Error 2
...

By changing kernel/time.c to include linux/mm.h, the build succeeds.

Signed-off-by: Jesper Nilsson <jesper.nilsson@axis.com>
Cc: Mikael Starvik <mikael.starvik@axis.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>