ARM: dts: imx5: add gpu nodes

This adds the gpu nodes for the adreno 200 GPU on iMX51 and iMX53, now
supported by the freedreno driver.

The compatible for the iMX51 uses a patchid of 1, which is used by drm/msm
driver to identify the smaller 128KiB GMEM size.

Signed-off-by: Jonathan Marek <jonathan@marek.ca>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>