fix SH7705_CACHE_32KB compilation

This patches compile errors like the following caused by
commit 51f3547d
(sh: Allow SH-3 and SH-5 to use common headers):

<--  snip  -->

...
  CC      arch/sh/mm/init.o
/home/bunk/linux/kernel-2.6/git/linux-2.6/arch/sh/mm/init.c: In function 'mem_init':
/home/bunk/linux/kernel-2.6/git/linux-2.6/arch/sh/mm/init.c:232: error: implicit declaration of function 'p3_cache_init'
make[2]: *** [arch/sh/mm/init.o] Error 1
make[1]: *** [arch/sh/mm] Error 2
...
  CC      kernel/fork.o
/home/bunk/linux/kernel-2.6/git/linux-2.6/kernel/fork.c: In function 'dup_mmap':
/home/bunk/linux/kernel-2.6/git/linux-2.6/kernel/fork.c:323: error: implicit declaration of function 'flush_dcache_mmap_lock'
/home/bunk/linux/kernel-2.6/git/linux-2.6/kernel/fork.c:325: error: implicit declaration of function 'flush_dcache_mmap_unlock'
make[2]: *** [kernel/fork.o] Error 1

<--  snip  -->

Reported-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>