drm/radeon/kms/DCE4.1: fix Select_CrtcSource EncodeMode setting for DP bridges (v2)

Settings in this table reflect the physical panel/connector rather
than the internal dig encoding.

v2: fix typo for DRM_MODE_CONNECTOR_VGA case.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>