drm/amd/display: fill in clock values when DPM is not enabled

[Why]
For individual feature testing, PMFW may not report all clock
values back. Driver will default them to 0 but this will
cause the BB table to be skipped and default to one state
with max clocks.

[How]
Add helper function to scan through initial clock values and
populate them with default clock limits so that BB table
can be built.
Add dpm_enabled flag to check when DPM is not enabled and
to trigger helper function.

Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Jasdeep Dhillon <jdhillon@amd.com>
Signed-off-by: Samson Tam <samson.tam@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>