Check result of find_mmc_device() before calling mmc_init().
This patch avoid a data abort when the command try to acces
to sd/mmc device deactivated in device tree.
Fixes: aff4c5dd82 ("stm32mp: stm32prog: add MMC device")
Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@st.com>