drm/i915/mtl: C20 HW readout

drm/i915/mtl: C20 HW readout

Create a table for C20 DP1.4, DP2.0 and HDMI2.1 rates.
The PLL settings are based on table, not for algorithmic alternative.
For DP 1.4 only MPLLB is in use.

Once register settings are done, we read back C20 HW state.

BSpec: 64568

v2: Updated pll tables (RK)
    MPLLB selection fix (RK)

Signed-off-by: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Arun R Murthy <arun.r.murthy@intel.com>
Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Reviewed-by: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Signed-off-by: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230428095433.4109054-3-mika.kahola@intel.com