The Allwinner F1C100s series of SoCs contain a LRADC (aka. KEYADC)
compatible to the version in other SoCs.
The manual doesn't mention the ratio of the input voltage that is used,
but comparing actual measurements with the values in the register
suggests that it is 3/4 of Vref.

Add an F1C100s compatible string to the list, and pair it with the
A83T fallback. Since the A64 is the same, combined both using an enum.
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20221101141658.3631342-9-andre.przywara@arm.comSigned-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>