ARM: imx_v6_v7_defconfig: enable the vf610 gpio driver

The vf610 gpio driver is used in i.MX7ULP chips (Cortex A7, ARMv7-A
architecture). Enable it in imx_v6_v7_defconfig.

(vf610 gpio used to be enabled by default for all i.MX chips. This was
changed recently as most i.MX chips don't need this driver.)

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>