mmc: sdhci-of-arasan: add phy support for sdhci-of-arasan

This patch adds Generic PHY access for sdhci-of-arasan. Driver
can get PHY handler from dt-binding, and power-on/init the PHY.
Currently, it's just mandatory for arasan,sdhci-5.1.

Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>