drm/amd/display: Fix dual eDP abnormal display issue

[WHY]
Driver use primary eDP link stream as the condition
to enable fastboot or not.
In dual eDP case, set second screen only,
this would cause slave eDP timing to be used on primary one.

[HOW]
Add a check for unmatched eDP link stream.

Reviewed-by: Nicholas Kazlauskas <Nicholas.Kazlauskas@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Brandon Syu <Brandon.Syu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>