dt-bindings: mmc: sunxi: add Allwinner F1c100s compatible

The Allwinner F1C100 series contains two MMC controller blocks. From
comparing the data sheets, they seem to be compatible with the one used
in the Allwinner A20: the register layout is the same, and they use the
same separate sample and output clocks design.
The only difference is the missing reset line in the A20 version, but
both the binding and the Linux driver make this optional, so it's still
a fit.

Add the new SoC specific name and require it to be paired with the A20
fallback name, as this is all the driver needs to care about.

Signed-off-by: Jesse Taube <Mr.Bossman075@gmail.com>
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Samuel Holland <samuel@sholland.org>
Link: https://lore.kernel.org/r/20220307143421.1106209-8-andre.przywara@arm.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>