commit 1d33e1fc upstream.

Return the encoder id rather than a boolean.  This is needed
for differentiate between multiple DP bridge chips.
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>