armv4: add a stub for dcache_line_bytes()

This adds a stub for dcache_line_bytes() that returns a hard-coded
value for now. The actual value won't matter until we try to turn
on caching in the bootblock (if ever).

BUG=none
BRANCH=none
TEST=tested on nyan

Change-Id: I3876e8282698cc860ddd7b65e58246d8095958bd
Signed-off-by: David Hendricks <dhendrix@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/173976
Reviewed-by: Gabe Black <gabeblack@chromium.org>

src/arch/arm/armv4/cache.c

@@ -55,6 +55,17 @@ void dcache_invalidate_all(void)
 {
 }
 
+unsigned int dcache_line_bytes(void)
+{
+	/*
+	 * TODO: Implement this correctly. For now we just return a
+	 * reasonable value. It was added during Nyan development and
+	 * may be used in bootblock code. It matters only if dcache is
+	 * turned on.
+	 */
+	return 64;
+}
+
 void dcache_clean_by_mva(void const *addr, size_t len)
 {
 }

src/arch/arm/include/armv4/arch/cache.h

@@ -57,6 +57,9 @@ void dcache_clean_all(void);
 /* dcache invalidate all (on current level given by CCSELR) */
 void dcache_invalidate_all(void);
 
+/* returns number of bytes per cache line */
+unsigned int dcache_line_bytes(void);
+
 /* dcache and MMU disable */
 void dcache_mmu_disable(void);