i810fb: fix incorrect frequency mask

Fix a long-standing bug.  The mask used to detect a 100Mhz or 133Mhz chipset
is incorrect. (The only side effect of this bug is that it will choose an
incorrect watermark).
Signed-off-by: NAntonino Daplas <adaplas@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/video/i810/i810.h

@@ -133,7 +133,7 @@
 /* Masks (AND ops) and OR's */
 #define FB_START_MASK               (0x3f << (32 - 6))
 #define MMIO_ADDR_MASK              (0x1FFF << (32 - 13))
-#define FREQ_MASK                   0x1EF
+#define FREQ_MASK                   (1 << 4)
 #define SCR_OFF                     0x20
 #define DRAM_ON                     0x08            
 #define DRAM_OFF                    0xE7