BACKPORT: drm/dp_mst: Parse FEC capability on MST ports

As of DP1.4, ENUM_PATH_RESOURCES returns a bit indicating
if FEC can be supported up to that point in the MST network.

The bit is the first byte of the ENUM_PATH_RESOURCES ack reply,
bottom-most bit (refer to section 2.11.9.4 of DP standard,
v1.4)

That value is needed for FEC and DSC support

Store it on drm_dp_mst_port

Reviewed-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: David Francis <David.Francis@amd.com>
Signed-off-by: Mikita Lipski <mikita.lipski@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit a3c2b0ffc007e5d98f5313ed951fff092535fb6d)
Bug: 152417756
Signed-off-by: Alistair Delva <adelva@google.com>
Change-Id: Ie5b5d16aec40b36e58fda0d1a8aa58aa85fdd984