riscv: starfive: jh7110: move uart0 clock frequency to config header

riscv: starfive: jh7110: move uart0 clock frequency to config header

Move unnecessary clock frequency assignment out of device-tree and into the
board config header so that the ns16550 serial driver can successfully init
during SPL after failing to resolve the parent clock from upstream dts. The
serial driver will then resolve clock frequency from device-tree node parent
clock at init during Main app as it is expected by upstream.

Signed-off-by: E Shattow <e@freeshell.de>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>