drm/amd/display: Providing a mechanism to have a custom pwm frequency

[Why]
Providing a mechanism to manipulate the pwm frequency on the
individual GPUs and monitor the transition during the switch.

[How]
Added a variable in dc_debug_options data structure. Using
this variable to call the newly added command on the firmware.

Reviewed-by: Harry Vanzylldejong <harry.vanzylldejong@amd.com>
Acked-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Sreeja Golui <sreeja.golui@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>