[RADEON]: Fix unaligned I/O port access during probe.

The driver does a readl() on DEVICE_ID which is 2-byte aligned and
2-bytes in size.  It's doing this read just to flush write buffers.

Create IN16() and OUT16() macros, and use the former to do this I/O
load.

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/video/aty/radeon_base.c b/drivers/video/aty/radeon_base.c
index 046b478..8a24a66 100644
--- a/drivers/video/aty/radeon_base.c
+++ b/drivers/video/aty/radeon_base.c
@@ -475,7 +475,7 @@
 	 */
 
 	/* Flush PCI buffers ? */
-	tmp = INREG(DEVICE_ID);
+	tmp = INREG16(DEVICE_ID);
 
 	local_irq_disable();