drm/radeon/kms: Report vga connector is connected according to ddc_probe

On broken EDID we were reporting vga connector to be disconnected
even if ddc probe did found a monitor. This patch report that the
connector is connected on such case. This allow drm to add a fail
safe mode (800x600 at the time of this patch) thus user can boot
and later add a mode which match its monitor capabilities.

Signed-off-by: Jerome Glisse <jglisse@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>