mmc: mv_sdhci: parse device-tree entry

Call mmc_of_parse() so that generic DT properties like 'non-removable'
are taken into account.

This fixes boot on Clearfog with eMMC on SOM that requires the
non-removable property.

Reported-by: Thorsten Spille <thorsten_spille@netcor.de>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>
Reviewed-by: Marek Behún <marek.behun@nic.cz>