dm: mmc: sunxi: Drop mmc_clk_io_on()

This function has #ifdefs in it which we want to avoid for driver model.
Instead we should use different compatible strings and the .data field.
It also uses the MMC device number which is not available in driver
model except through aliases.

Move the function's into its caller so that the driver-model version can
do things its own way.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>