spidev warning fix

Git rid of "warning: passing arg 2 of `access_ok' makes pointer from integer
without a cast" reported on SH ...  most architectures use macros in that
test, SH uses inlined functions.
Signed-off-by: NDavid Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/spi/spidev.c

@@ -183,7 +183,9 @@ static int spidev_message(struct spidev_data *spidev,
 
 		if (u_tmp->rx_buf) {
 			k_tmp->rx_buf = buf;
-			if (!access_ok(VERIFY_WRITE, u_tmp->rx_buf, u_tmp->len))
+			if (!access_ok(VERIFY_WRITE, (u8 __user *)
+						(ptrdiff_t) u_tmp->rx_buf,
+						u_tmp->len))
 				goto done;
 		}
 		if (u_tmp->tx_buf) {