ARM: imx_v6_v7_defconfig: Enable GPIO_74X164

imx7d-sabresd board uses a 74LV595PW SPI expander to drive several
peripherals, such as Ethernet reset, PCI reset, LCD power, etc.

Enabled this option by default.

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>