pinctrl: baytrail: Fix compilation warnings when !CONFIG_PM

pinctrl: baytrail: Fix compilation warnings when !CONFIG_PM

When CONFIG_PM is not set we get following compilation warnings:

 warning: ‘byt_gpio_runtime_suspend’ defined but not used [-Wunused-function]
 warning: ‘byt_gpio_runtime_resume’ defined but not used [-Wunused-function]

Fix this by guarding byt_gpio_runtime_suspend()/byt_gpio_runtime_resume()
with #ifdef CONFIG_PM.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>