mmc: sunxi: Convert MMC driver to the standard clock phase API

Now that we have proper support to use the generic phase API in our clock
driver, switch the MMC driver to use it.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Acked-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: David Lanzendörfer <david.lanzendoerfer@o2s.ch>
Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Tested-by: Chen-Yu Tsai <wens@csie.org>