ARM: imx_v4_v5_defconfig: Enable gpio regulator and gpio button/keyboard.

The eukrea mbimxsd25 has a gpio regulator for enabling its
  LCD display, it also has a gpio button.

We enable the respective drivers in order to be able to use theses
  features with this configuration.

Cc: Sascha Hauer <kernel@pengutronix.de>
Cc: linux-arm-kernel@lists.infradead.org
Cc: Fabio Estevam <fabio.estevam@freescale.com>
Cc: Eric Bénard <eric@eukrea.com>
Signed-off-by: Denis Carikli <denis@eukrea.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>