mmc: host: omap_hsmmc: use ios->vdd for setting vmmc voltage

vdd voltage is set in mmc core to ios->vdd and vmmc should actually
be set to this voltage. Modify omap_hsmmc_enable_supply
to not take vdd as argument since now it's directly set to
the voltage in ios->vdd.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Tested-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>