drm/amd/display: Update to correct min FCLK when construction BB

[Description]
- For min FCLK, choose the min of 300Mhz and PMFW requirement
- Also only apply min DET check in DML for non-UR cases

Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Alvin Lee <Alvin.Lee2@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>