drm/amd/display: Use dcfclk to populate watermark ranges

[WHY & HOW]
Previously drain clk was unconstrained and fill clk was constrained on fclk.
We want to change it to fill clk unconstrained and drain clock constrained
to dcfclk.

Signed-off-by: Sung Lee <sung.lee@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>