ARM: imx_v6_v7_defconfig: Select CONFIG_IMX7D_ADC

Select CONFIG_IMX7D_ADC so that the i.MX7 ADC driver can be
built by default.
Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/configs/imx_v6_v7_defconfig

@@ -345,6 +345,7 @@ CONFIG_IMX_SDMA=y
 CONFIG_MXS_DMA=y
 CONFIG_STAGING=y
 CONFIG_IIO=y
+CONFIG_IMX7D_ADC=y
 CONFIG_VF610_ADC=y
 CONFIG_MPL3115=y
 CONFIG_PWM=y