drm/amd/display: Add a new dcdebugmask to allow skip detection LT

drm/amd/display: Add a new dcdebugmask to allow skip detection LT

Under specific embedded scenarios, we might still use DP interface
rather than eDP interface. Under such case, detection link training
is unnecessary.

Add a new dcdebugmask value that can be used to skip the detection LT

Reviewed-by: Tom Chung <chiahsuan.chung@amd.com>
Link: https://lore.kernel.org/amd-gfx/20250521063934.2111323-1-Wayne.Lin@amd.com/
Signed-off-by: Wayne Lin <Wayne.Lin@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>