ARC: Use enough bits for determining page's cache color

The current code uses 2 bits for determining page's dcache color, thus
sorting pages into 4 bins, whereas the aliasing dcache really has 2 bins
(8k page, 64k dcache - 4 way-set-assoc).
This can cause extraneous flushes - e.g. color 0 and 2.
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

arch/arc/include/asm/cacheflush.h

@@ -93,7 +93,7 @@ static inline int cache_is_vipt_aliasing(void)
 #endif
 }
 
-#define CACHE_COLOR(addr)	(((unsigned long)(addr) >> (PAGE_SHIFT)) & 3)
+#define CACHE_COLOR(addr)	(((unsigned long)(addr) >> (PAGE_SHIFT)) & 1)
 
 /*
  * checks if two addresses (after page aligning) index into same cache set