tty: serial: meson: Drop the legacy compatible strings and clock code

All mainline .dts files have been using the stable UART since Linux
4.16. Drop the legacy compatible strings and related clock code.

Signed-off-by: Yu Tu <yu.tu@amlogic.com>
Link: https://lore.kernel.org/r/20211230102110.3861-2-yu.tu@amlogic.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>