MAINTAINERS: update drm bug reporting URL

The original bugzilla seems to be read-only now, linking to the gitlab
for new bugs.

Signed-off-by: Pavel Turinský <[email protected]>
Cc: [email protected]
Signed-off-by: Daniel Vetter <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
Signed-off-by: Maarten Lankhorst <[email protected]>

MAINTAINERS

@@ -5835,7 +5835,7 @@ M:	David Airlie <[email protected]>
 M:	Daniel Vetter <[email protected]>
 L:	[email protected]
 S:	Maintained
-B:	https://bugs.freedesktop.org/
+B:	https://gitlab.freedesktop.org/drm
 C:	irc://chat.freenode.net/dri-devel
 T:	git git://anongit.freedesktop.org/drm/drm
 F:	Documentation/devicetree/bindings/display/