samples: usb: hid-mouse: enable CONFIG_GPIO
samples: usb: hid-mouse: enable CONFIG_GPIO

The HID mouse sample uses the GPIO to read the state of a button, but
does not enable CONFIG_GPIO, causing the example to fail. Fix that.

Signed-off-by: Aurelien Jarno <bceb368e7f2cb351af47298f32034f0587bbe4a6@aurel32.net>

explora26/zephyr,punitvara/zephyr,GiulianoFranchetto/zephyr,finikorg/zephyr,finikorg/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,punitvara/zephyr,nashif/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,galak/zephyr,punitvara/zephyr,ldts/zephyr,nashif/zephyr,finikorg/zephyr,explora26/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,finikorg/zephyr,ldts/zephyr,ldts/zephyr,GiulianoFranchetto/zephyr,galak/zephyr,GiulianoFranchetto/zephyr,galak/zephyr,nashif/zephyr,Vudentz/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,punitvara/zephyr,explora26/zephyr,galak/zephyr,explora26/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,punitvara/zephyr,Vudentz/zephyr,explora26/zephyr,ldts/zephyr,ldts/zephyr