board: starfive: Remove compatible boards Milk-V Mars CM and Mars CM Lite

board: starfive: Remove compatible boards Milk-V Mars CM and Mars CM Lite

Remove leftover code from Milk-V Mars CM and Mars CM Lite boards that do
not exist in upstream Linux Kernel devicetree-rebasing. These will be re-
introduced when submitted upstream for a future U-Boot release. Users of
these boards should use the previous stable release of U-Boot until then.

Signed-off-by: E Shattow <e@freeshell.de>