drm/i915/tc: Group the TC PHY setup/query functions per platform

Arrange the TC PHY HW state setup/query functions into platform
specific and generic groups. This prepares for upcoming patches adding
generic TC PHY handlers and platform specific hooks for these,
replacing the corresponding if ladders.

No functional changes.

v2: Fix non kernel-doc multiline comments. (Jani)

Cc: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230323142035.1432621-2-imre.deak@intel.com