Add Device Tree binding document for the NVIDIA Tegra234 pinmux controller. Bug 3621816 Change-Id: Ide78ac3bccbce341afe1e648d901e4f0ffb27bdf Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com> Reviewed-on: https://git-master.nvidia.com/r/c/linux-nv-oot/+/2704710 GVS: Gerrit_Virtual_Submit