drm/amd/display: Refactor DSC cap calculations

[WHY]
DSC block level should only be responsible for reporting single DSC
instance capabilities. Factoring in ODM combine requirements should be
handled in dc_dsc.c. Both components should acquire clocks from clk_mgr
to determine throughput capabilities instead of relying on hard coded
values as these can differ by SoC and SKU.

[HOW]
1) Add dsc_get_single_enc_caps to acquire single DSC instance
    capabilities (replacing dsc_get_enc_caps), factoring in DSCCLK
2) add build_dsc_enc_caps to combine single DSC instance capabilities
3) account for max pixel rate per pipe (DISPCLK) when calculating
    minimum slice count

Reviewed-by: Wenjing Liu <wenjing.liu@amd.com>
Signed-off-by: Dillon Varone <dillon.varone@amd.com>
Signed-off-by: Ivan Lipski <ivan.lipski@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>