drm/amd/display: FCLK P-state support updates

[Why]
Previously we used to send FCLK P-state enable messages upon each call
to update_clocks based on dml output. This resulted in increased message
transactions between DC and PMFW.

[How]
Update the code to check safe_to_lower status and send the message based
on dml input only on boot. This reduces message transactions. Also
remove other unwanted code based on current code status.

Signed-off-by: Chaitanya Dhere <chaitanya.dhere@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>