drm/nv50-/disp: remove dcb_outp_match call, and related variables

commit 9a7046d55f319b2dde5d2536cc2adb01ebdbe09e upstream.

Unused and irrelavant since the code move of DP training/linkcontrol interrupt

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Cc: Ilia Mirkin <imirkin@alum.mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>