glx: Keep display fd open for prime

glx: Keep display fd open for prime

Keep the display fd open for creating DRI screen on display gpu in
case of prime.

v2: initialize psc->fd_display_gpu early (Michel Dänzer)
    fix display gpu fd leakage (Michel Dänzer)
v3: fix more display gpu fd leakage (Michel Dänzer)

Signed-off-by: Yogesh Mohanmarimuthu <yogesh.mohanmarimuthu@amd.com>
Acked-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Reviewed-by: Michel Dänzer <mdaenzer@redhat.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10595>