drm/i915/tc: Add TC PHY hook to init the PHY

Add a hook for platform specific PHY initialization. Move the detection
of modular FIAs to the TGL handler, skipping this on ADLP+ where the
FIAs are always modular, not requiring a detection.

Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230323142035.1432621-22-imre.deak@intel.com