NVIDIA's Tegra SoCs have the matrix keyboard controller which
supports 16x8 type of matrix. The number of rows and columns
are configurable.

Add DT entry for KBC controller.
Signed-off-by: NLaxman Dewangan <ldewangan@nvidia.com>
[swarren: added clocks property]
Signed-off-by: NStephen Warren <swarren@nvidia.com>