ata_if_xfermask() word 51 fix

If word 53 bit 1 isn't set, the maximum PIO mode is indicated by
the upper 8 bits of word 51, not the lower 8 bits.  Fixes PIO mode
detection on old Compact Flash cards.
Signed-off-by: NLennert Buytenhek <buytenh@wantstofly.org>
Signed-off-by: NJeff Garzik <jeff@garzik.org>

drivers/ata/libata-core.c

@@ -1037,7 +1037,7 @@ static unsigned int ata_id_xfermask(const u16 *id)
 		 * the PIO timing number for the maximum. Turn it into
 		 * a mask.
 		 */
-		u8 mode = id[ATA_ID_OLD_PIO_MODES] & 0xFF;
+		u8 mode = (id[ATA_ID_OLD_PIO_MODES] >> 8) & 0xFF;
 		if (mode < 5)	/* Valid PIO range */
                 	pio_mask = (2 << mode) - 1;
 		else