drivers/staging/speakup: fix indent coding style problem in spk_ttyio.c

This is a patch to the spk_ttyio.c file which fixes up the indent error
reported by the checkpatch.pl tool.
Signed-off-by: NRui Teng <rui.teng@linux.vnet.ibm.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/speakup/spk_ttyio.c

@@ -61,7 +61,7 @@ static int spk_ttyio_receive_buf2(struct tty_struct *tty,
 		return 0;
 
 	/* Make sure the consumer has read buf before we have seen
-         * buf_free == true and overwrite buf */
+	 * buf_free == true and overwrite buf */
 	mb();
 
 	ldisc_data->buf = cp[0];