drm/i915/cx0: Enable dpll framework for MTL+

drm/i915/cx0: Enable dpll framework for MTL+

MTL+ platforms are supported by dpll framework remove a separate
check for hw comparison and rely solely on dpll framework
hw comparison.

Finally, all required hooks are now in place so initialize
PLL manager for MTL+ platforms and remove the redirections
to the legacy code paths from the following interfaces:

* intel_encoder::clock_enable/disable()
* intel_encoder::get_config()
* intel_dpll_funcs::get_hw_state()
* intel_ddi_update_active_dpll()
* pipe_config_pll_mismatch()

v2: Rebase on !HAS_LT_PHY check in intel_ddi_update_active_dpll()
v3: Rebase on !display->dpll.mgr check in intel_ddi_update_active_dpll()
    Add check for NVL as the platform is not part of pll framework (Suraj)

Signed-off-by: Mika Kahola <mika.kahola@intel.com>
Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
Link: https://lore.kernel.org/r/20251118132859.2584452-1-mika.kahola@intel.com