ARM: imx_v6_v7_defconfig: add CONFIG_I2C_GPIO

The GPIO-based bitbanging I2C driver is required to make HDMI work on
the Apalis iMX6 module plugged into a Ixora carrier board featuring a
DDC channel to read a screen's EDID being hooked up to regular GPIOs.

Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>