dt-bindings: watchdog: sunxi: clarify clock support

Most Allwinner SoCs have just one input clock to drive the watchdog
peripheral. So far this is the 24 MHz "HOSC" oscillator, divided down
internally to 32 KHz.
The F1C100 series watchdog however uses the unchanged 32 KHz "LOSC" as
its only clock input, which has the same effect, but let's the binding
description mismatch.

Change the binding description to name the clocks more loosely, so both
the LOSC and divided HOSC match the description. As the fixed clock names
now make less sense, drop them from SoCs supporting just one clock
input, they were not used by any DT anyway.

For the newer SoCs, supporting a choice of two input clocks, we keep
both the description and clock-names requirement.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Samuel Holland <samuel@sholland.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Link: https://lore.kernel.org/r/20220317162349.739636-3-andre.przywara@arm.com