st/va: implement VaCreateSurfaces2 and VaQuerySurfaceAttributes

st/va: implement VaCreateSurfaces2 and VaQuerySurfaceAttributes

Inspired from http://cgit.freedesktop.org/vaapi/intel-driver/
especially src/i965_drv_video.c::i965_CreateSurfaces2.

This patch is mainly to support gstreamer-vaapi and tools that uses
this newer libva API. The first advantage of using VaCreateSurfaces2
over existing VaCreateSurfaces, is that it is possible to select which
the pixel format for the surface. Indeed with the simple VaCreateSurfaces
function it is only possible to create a NV12 surface. It can be useful
to create a RGBA surface to use with video post processing.

The avaible pixel formats can be query with VaQuerySurfaceAttributes.

Signed-off-by: Julien Isorce <j.isorce@samsung.com>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Christian König <christian.koenig@amd.com>