imx: Fix regression with CONFIG_DM_MMC=y

imx: Fix regression with CONFIG_DM_MMC=y

When CONFIG_DM_MMC=y, CONFIG_BLK should be selected, otherwise the
SD/eMMC card cannot be used.

Also, select CONFIG_DM_USB=y when CONFIG_USB=y to avoid build failure.

Tested on mx6slevk, mx7dsabresd and mx6ullevk.

Signed-off-by: Fabio Estevam <[email protected]>
Reviewed-by: Jaehoon Chung <[email protected]>
Tested-by: Adam Ford <[email protected]>
Tested-by: Sébastien Szymanski <[email protected]>
Tested-by: Jagan Teki <[email protected]>
Reviewed-by: Jagan Teki <[email protected]>