drm/i915/mtl: Skip PLL state verification in TBT mode

In TBT-alt mode the driver doesn't program the PHY's PLL, which is
handled instead by Thunderbolt driver/FW components, hence the PLL's HW
vs. SW state verification should be skipped. During HW readout set a flag
in the PLL state if the port was at the moment in TBT-alt mode and skip
the verification of PLL parameters in this case.

Fixes: 45fe957a

 ("drm/i915/display: Add compare config for MTL+ platforms")
Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/11258
Cc: Mika Kahola <mika.kahola@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/20240626170813.806470-1-imre.deak@intel.com