pinctrl: lynxpoint: Introduce helpers to enable or disable input

Introduce couple of helpers to enable or disable input. i.e.
lp_gpio_enable_input() and lp_gpio_disable_input().

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>