Fix Kconfig warning for PCENGINES_APU2 symbol:

WARNING: unmet direct dependencies detected for GPIO_AMD_FCH
  Depends on [n]: GPIOLIB [=n] && HAS_IOMEM [=y]
  Selected by [y]:
  - PCENGINES_APU2 [=y] && X86 [=y] && X86_PLATFORM_DEVICES [=y] && INPUT [=y] && INPUT_KEYBOARD [=y] && LEDS_CLASS [=y]

WARNING: unmet direct dependencies detected for KEYBOARD_GPIO_POLLED
  Depends on [n]: !UML && INPUT [=y] && INPUT_KEYBOARD [=y] && GPIOLIB [=n]
  Selected by [y]:
  - PCENGINES_APU2 [=y] && X86 [=y] && X86_PLATFORM_DEVICES [=y] && INPUT [=y] && INPUT_KEYBOARD [=y] && LEDS_CLASS [=y]

Add GPIOLIB dependency to fix it.
Reported-by: Hulk Robot <hulkci@huawei.com>
Fixes: f8eb0235 ("x86: pcengines apuv2 gpio/leds/keys platform driver")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>