Input: matrix_keyboard - remove linux/gpio.h inclusion

linux/gpio.h is going away, so remove that since the driver already
includes linux/gpio/consumer.h.

Acked-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://patch.msgid.link/20260710211954.1373336-10-arnd@kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>