ARM: dts: aspeed-g6: Enable more UART controllers

Setup the configuration of UART6, UART7, UART8, and UART9 in
aspeed-g6.dtsi.

Signed-off-by: Ken Chen <j220584470k@gmail.com>
Link: https://lore.kernel.org/r/20220805090957.470434-1-j220584470k@gmail.com


Signed-off-by: Joel Stanley <joel@jms.id.au>