sc16is7xx: enable the clock

Although clk_disable_unprepare() is called both on .remove()
and in .probe() error path, the clock is never actually enabled.
Signed-off-by: NJakub Kicinski <kubakici@wp.pl>
Signed-off-by: NJon Ringle <jringle@gridpoint.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/sc16is7xx.c

@@ -1050,6 +1050,7 @@ static int sc16is7xx_probe(struct device *dev,
 		else
 			return PTR_ERR(s->clk);
 	} else {
+		clk_prepare_enable(s->clk);
 		freq = clk_get_rate(s->clk);
 	}