arm64: dts: rockchip: Describe RK3328 GPIO_MUTE users

Add explicit properties to describe existing boards' GPIO_MUTE usage
for the analog codec.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/53637c0359ad9473dc1391a8428ba21017ec467e.1581376744.git.robin.murphy@arm.com


Signed-off-by: Heiko Stuebner <heiko@sntech.de>