drm/amd/display: Make dcn401_initialize_min_clocks() available to other compilation units

[Why & How]
Expose dcn401_initialize_min_clocks() for future use and add additional
check for IP register.

Reviewed-by: Nevenko Stupar <nevenko.stupar@amd.com>
Signed-off-by: Karthi Kandasamy <karthi.kandasamy@amd.com>
Signed-off-by: Ivan Lipski <ivan.lipski@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>