drm/i915/tc: Add TC PHY hook to read out the PHY HW state

Add a TC PHY hook to read out the PHY HW state on each platform, move
the common parts to the generic helper.

Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230323142035.1432621-11-imre.deak@intel.com