ARM: imx_v6_v7_defconfig: Select CONFIG_SND_SOC_WM8962 explicitly

Currently CONFIG_SND_SOC_WM8962 is selected via SND_SOC_IMX_WM8962
machine driver option.

SND_SOC_IMX_WM8962 will be removed in the next kernel cycle, so
select the codec driver directly so that it can still be used
by default via the generic fsl-asoc-card machine driver.

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