drm/amd/display: Add crtc matching and panel type tests for connector

drm/amd/display: Add crtc matching and panel type tests for connector

Add KUnit coverage for amdgpu_dm_find_first_crtc_matching_connector():
match, no match, empty state, skipping NULL connector slots, and
returning the first match when several target the same crtc.

Also add coverage for amdgpu_dm_set_panel_type(): VSDB OLED/miniLED,
DPCD OLED/miniLED, Samsung miniLED above and below threshold, and the
default LCD fallback.

Assisted-by: Copilot:Claude-Opus-4.8
Reviewed-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Bhawanpreet Lakha <bhawanpreet.lakha@amd.com>
Signed-off-by: George Zhang <george.zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>