drm/i915/hdmi: C20 computed PLL frequencies

Use algorithm to generate HDMI C20 PLL clock frequencies.

v2: checkpatch fixes

BSPEC: 64568
Cc: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Cc: Mika Kahola <mika.kahola@intel.com>
Cc: Anusha Srivatsa <anusha.srivatsa@intel.com>
Reviewed-by: Gustavo Sousa <gustavo.sousa@intel.com>
Signed-off-by: Clint Taylor <clinton.a.taylor@intel.com>
[mattrope: Wrapped one overly long line]
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230515231725.3815199-3-clinton.a.taylor@intel.com