mmc: omap: Remove mem_res field from struct mmc_omap_host

Field mem_res in struct mmc_omap_host is used only once in mmc_omap_probe
when setting the phys_base field so we may just se the phys_base straight
and remove needless mem_res.

Signed-off-by: Jarkko Nikula <jarkko.nikula@bitmer.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Tested-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Chris Ball <chris@printf.net>