serial: 8250: Don't check for mctrl_gpio_init() returning -ENOSYS

Now that the mctrl_gpio code returns NULL instead of ERR_PTR(-ENOSYS)
if CONFIG_GPIOLIB is disabled, we can safely remove this check.

Signed-off-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Acked-by: Uwe Kleine-Knig <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20190802100349.8659-4-frieder.schrempf@kontron.de


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>