Documentation/spi/* compile warning fix

Fix this warning:

Documentation/spi/spidev_fdx.c: In function `do_msg':
Documentation/spi/spidev_fdx.c:61: warning: cast from pointer to integer of different size
Documentation/spi/spidev_fdx.c:64: warning: cast from pointer to integer of different size

buf should be unsigned long to match native arch on 32-bit x86 compile.
Signed-off-by: NPrarit Bhargava <prarit@redhat.com>
Signed-off-by: NGrant Likely <grant.likely@secretlab.ca>

Documentation/spi/spidev_fdx.c

@@ -58,10 +58,10 @@ static void do_msg(int fd, int len)
 		len = sizeof buf;
 
 	buf[0] = 0xaa;
-	xfer[0].tx_buf = (__u64) buf;
+	xfer[0].tx_buf = (unsigned long)buf;
 	xfer[0].len = 1;
 
-	xfer[1].rx_buf = (__u64) buf;
+	xfer[1].rx_buf = (unsigned long) buf;
 	xfer[1].len = len;
 
 	status = ioctl(fd, SPI_IOC_MESSAGE(2), xfer);