uboot-phytec

icorem6_rqs: env: Return mmc devno

Instead of changing mmc devno from dts nodes better
to return the detected devno so-that env trigger the same.

Cc: Stefano Babic <sbabic@denx.de>
Cc: Tom Rini <trini@konsulko.com>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>