ARM64: dts: meson-axg: add pinctrl DT info for Meson-AXG SoC

Add new pinctrl DT info for the Amlogic's Meson-AXG SoC.

Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Xingyu Chen <xingyu.chen@amlogic.com>
Signed-off-by: Yixun Lan <yixun.lan@amlogic.com>
[khilman: dropped unnecessary include]
Signed-off-by: Kevin Hilman <khilman@baylibre.com>