drm/amd/display: Add dc_debug flag to disable min fclk

[Why&How]
Add debug flag for an option to disable min fclk.

Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>