ARM: dts: suniv: F1C100: fix CPU node

The /cpu node in the f1c100s.dtsi is not spec compliant, it's missing
the reg property, and the corresponding address and size cells
properties.

Add them to make the bindings check pass.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Link: https://lore.kernel.org/r/20220317162349.739636-7-andre.przywara@arm.com