dt-bindings: clock: Add documentation for MAC PHY control bindings.

Update the CGU binding documentation, add mac-phy-ctrl as a
pattern property.

Signed-off-by: 周琰杰 (Zhou Yanjie) <zhouyanjie@wanyeetech.com>
Acked-by: Paul Cercueil <paul@crapouillou.net>
Acked-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>