drm/nv50/disp: prevent false output detection on the original nv50
drm/nv50/disp: prevent false output detection on the original nv50

Commit ea9197cc323839ef3d5280c0453b2c622caa6bc7 effectively enabled the
use of an improved DAC detection code, but introduced a regression on
the original nv50 chipset, causing a ghost monitor to be detected.

v2 (Ben Skeggs): the offending line was likely a thinko, removed it for
all chipsets (tested nv50 and nve6 to cover entire range) and added
some additional debugging.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=67382
Tested-by: Martin Peres <f078f77bcd6141e84e4eefdc58402db4e0e36622@labri.fr>
Signed-off-by: Emil Velikov <4c996f2f093ddd0585a556460b4cc3ba555546ef@gmail.com>
Cc: <4fbacc2fa0ffdbb11bf1ad6925b886ebd08dd15f@vger.kernel.org> # 3.9+
Signed-off-by: Ben Skeggs <d9f27fb07c1e9f131223ad827fa5179f3846c30b@redhat.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs