ARM: dts: aspeed-g6: Add pinctrl settings

AST2600 supports 2 SGPIO master interfaces and 2 SGPIO slave interfaces.
Currently, only SGPIO master 1 and SGPIO slve 1 in the pinctrl dtsi.
SGPIO master 2 and slave 2 should be added in pinctrl dtsi as well.

Signed-off-by: Steven Lee <steven_lee@aspeedtech.com>
Reviewed-by: Andrew Jeffery <andrew@aj.id.au>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Joel Stanley <joel@jms.id.au>
Link: https://lore.kernel.org/r/20210525055308.31069-3-steven_lee@aspeedtech.com


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