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>

arch/sh/include/cpu-sh3/cpu/cacheflush.h

@@ -29,6 +29,16 @@ void flush_cache_page(struct vm_area_struct *vma, unsigned long addr, unsigned l
 void flush_dcache_page(struct page *pg);
 void flush_icache_range(unsigned long start, unsigned long end);
 void flush_icache_page(struct vm_area_struct *vma, struct page *page);
+
+#define flush_dcache_mmap_lock(mapping)		do { } while (0)
+#define flush_dcache_mmap_unlock(mapping)	do { } while (0)
+
+/* SH3 has unified cache so no special action needed here */
+#define flush_cache_sigtramp(vaddr)		do { } while (0)
+#define flush_icache_user_range(vma,pg,adr,len)	do { } while (0)
+
+#define p3_cache_init()				do { } while (0)
+
 #else
 #include <cpu-common/cpu/cacheflush.h>
 #endif