sh: rework nommu for generic cache.c use.

This does a bit of reorganizing for allowing nommu to use the new
and generic cache.c, no functional changes.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
diff --git a/arch/sh/include/asm/cacheflush.h b/arch/sh/include/asm/cacheflush.h
index 4bf621e..9ec13fb 100644
--- a/arch/sh/include/asm/cacheflush.h
+++ b/arch/sh/include/asm/cacheflush.h
@@ -76,5 +76,7 @@
 void *kmap_coherent(struct page *page, unsigned long addr);
 void kunmap_coherent(void);
 
+#define PG_dcache_dirty	PG_arch_1
+
 #endif /* __KERNEL__ */
 #endif /* __ASM_SH_CACHEFLUSH_H */