staging/rts_pstor: remove braces {} in sd.c (sd_pull_ctl_enable)

fixed below checkpatch warnings.
-WARNING: braces {} are not necessary for single statement blocks
Signed-off-by: Toshiaki Yamane <yamanetoshi@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rts_pstor/sd.c

@@ -2040,9 +2040,8 @@ int sd_pull_ctl_enable(struct rtsx_chip *chip)
 	}
 
 	retval = rtsx_send_cmd(chip, SD_CARD, 100);
-	if (retval < 0) {
+	if (retval < 0)
 		TRACE_RET(chip, STATUS_FAIL);
-	}
 
 	return STATUS_SUCCESS;
 }