xf86: dri2: Use va_gl as VDPAU driver for Intel i965 GPUs

The modesetting driver (which now often is used with Intel GPUs),
relies on DRI2ScreenInit() to setup the DRI and VDPAU driver names.

Before this commit it would always assign the same name to the 2 names,
but the VDPAU driver for i965 GPUs should be va_gl.

This commit adds a special case for the i965 case, replacing the
VDPAU driver name with "va_gl" if the GPU is using the i965 driver
for DRI.

Note this commit adds a FIXME comment for a related memory leak, that leak
was already present and fixing it falls outside of the scope of this commit.

BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=1413733
Cc: kwizart@gmail.com
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
3 jobs for i965-vdpau_driver in 6 minutes and 27 seconds (queued for 36 seconds)