drm/amd/display: Skip DPIA-specific DP LL automation flag for non-DPIA links

[Why]
The is_automated flag logic only applies to USB4 DPIA links during DP LL
compliance test automation. The flag should not be set for non-DPIA
cases.

[How]
Add check for DPIA link endpoint type before setting the flag. Also,
rename is_automated to skip_fallback_on_link_loss for clarity.

Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Reviewed-by: Meenakshikumar Somasundaram <meenakshikumar.somasundaram@amd.com>
Reviewed-by: Wenjing Liu <wenjing.liu@amd.com>
Acked-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Signed-off-by: George Shen <george.shen@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>