drm/amd/display: pass calculated dram_speed_mts to dml2

[why]
currently dml2 is using a hard coded 16 to convert memclk to dram_speed_mts.
for apu, this depends on wck_ratio.

change to pass the already calculated dram_speed_mts from fpu to dml2.

v2: use existing calculation of dram_speed_mts for now to avoid regression

Signed-off-by: Charlene Liu <Charlene.Liu@amd.com>
Signed-off-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Reviewed-by: Roman Li <Roman.Li@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>