vaapi: Add GEM buffer support
Submitted by wangfei
This is an Intel feature requirement.
The video driver's vaCreateSurfaces2 driver entrypoint shall accept a VASurfaceAttribMemoryType attribute value of VA_SURFACE_ATTRIB_MEM_TYPE_KERNEL_PRIME. This attribute will instruct the driver to use the buffer whose Prime file descriptor is stored in the VASurfaceAttribExternalBufferDescriptor as the backing buffer for the new VASurface.