drirc: Add sddm-greeter to adaptive_sync blacklist.

This is the sddm login screen.

Fixes: a9c36dbf ("drirc: Initial blacklist for adaptive sync")
Signed-off-by: Mario Kleiner <mario.kleiner.de@gmail.com>
Cc: 19.0 <mesa-stable@lists.freedesktop.org>
Signed-off-by: Marek Olšák <marek.olsak@amd.com>
(cherry picked from commit afb15d14)