dts: bindings: ethernet: add st,stm32h5-ethernet compatible

Add the compatible for h5 series for ethernet. The h5 series needs
it own because the memory-regions property isn't currently supported
by the implementation.

Add the h5 compatible to stm32h563.dtsi, in mac node.

Adjust the description in h7 compatible to remove the mention of h5
series, as now h5 series has it's own.

Signed-off-by: Benjamin Klaric <benjamin.klaric01@gmail.com>