h8300: add missing L1_CACHE_SHIFT

To fix build error

lib/atomic64.c: In function 'lock_addr':
lib/atomic64.c:40:11: error: 'L1_CACHE_SHIFT' undeclared (first use in this function) lib/atomic64.c:40:11: note: each undeclared identifier is reported only once for each function it appears in

---
 arch/h8300/include/asm/cache.h |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

@@ -2,7 +2,8 @@
 #define __ARCH_H8300_CACHE_H
 
 /* bytes per L1 cache line */
-#define        L1_CACHE_BYTES  4
+#define        L1_CACHE_SHIFT  2
+#define        L1_CACHE_BYTES  (1 << L1_CACHE_SHIFT)
 
 /* m68k-elf-gcc  2.95.2 doesn't like these */