clk: sunxi: mod0: Introduce MMC proper phase handling

The MMC clock we thought we had until now are actually not one but three
different clocks.

The main one is unchanged, and will have three outputs:
  - The clock fed into the MMC
  - a sample and output clocks, to deal with when should we output/sample data
    to/from the MMC bus

The phase control we had are actually controlling the two latter clocks, but
the main MMC one is unchanged.

We can adjust the phase with a 3 bits value, from 0 to 7, 0 meaning a 180 phase
shift, and the other values being the number of periods from the MMC parent
clock to outphase the clock of.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>