arm64: tegra: Add VDD_GPU regulator to Jetson TX1

Add the VDD_GPU regulator (a GPIO-enabled PWM regulator) to the Jetson
TX1 board. This addition allows the GPU to be used provided the
bootloader properly enabled the GPU node.

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
[as pointed out by Thierry on IRC, nobody has reported a bug
 in the field, but using a new bootloader with a .dtb that
 has the incorrect data, it will crash on boot]
Fixes: 336f79c7 ("arm64: tegra: Add NVIDIA Jetson TX1 Developer Kit support")
Cc: stable@vger.kernel.org #v4.5+
Signed-off-by: Arnd Bergmann <arnd@arndb.de>