commit 13485794 upstream.

If ddc fails, presumably the i2c mux (and hopefully the signal
mux) are switched to the other GPU so don't fetch the edid from
the vbios so that the connector reports disconnected.

bug:
https://bugzilla.opensuse.org/show_bug.cgi?id=904417Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
[ luis: backported to 3.16:
  - dropped changes to radeon_connector_get_edid() ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>