st/vdpau: use dri3 to directly send the buffer to X(v2)

this avoids an extra copy which occurs in case of dri2

v1.1: fallback to dri2 if dri3 fails to initialize
v2: add PIPE_BIND_SCANOUT to output buffers as they will
    be send to X server directly (Michel)

Suggested-by: Christian König <christian.koenig@amd.com>
Tested-by: Andy Furniss <adf.lists@gmail.com>
Signed-off-by: Nayan Deshmukh <nayan26deshmukh@gmail.com>
2 files changed