dri/common: use sysconfdir when looking for drirc

Useful when locally installed mesa has more quirks than the system one.

Signed-off-by: Marcin Ślusarz <marcin.slusarz@gmail.com>
Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
3 files changed