MGS-2730 gpu-viv : Set Unique for Vivante DRM Driver

MGS-2730 gpu-viv : Set Unique for Vivante DRM Driver

1. unique need to be set to get proper busid.
   Vivante driver is very simple and does not use drm_dev_alloc
   which in turn calls drm_dev_set_unique.
   Use set_busid to set the unique.

   https://patchwork.kernel.org/patch/9182749/

2. driver_features = DRIVER_LEGACY added to do mmap of SHM.
   https://patchwork.kernel.org/patch/8694561/

fix the problem that X11 cannot work with 4.9 kernel upgrade

Signed-off-by: Prabhu Sundararaj <prabhu.sundararaj@nxp.com>