drm/i915/ltphy: Return true for TBT scenario during lt_phy_state compare

TBT PHY is enablement/disablement is handled by its own TBT module.
We do not play a big part in it's state management, that being take care
by it's own TBT modeule.
The PHY/PLL TypeC mode (TBT, DP-alt) can change after the PLL state was
computed for a modeset, so the state verification after the modeset
sequence would indicate a mismatch in case the mode changed from DP-alt
to TBT, or from TBT to DP-alt mode. To avoid such a mismatch error the
verification is skipped if the mode for either the read-out or the
computed state is TBT (where that TBT PLL state doesn't reflect anyway
the PLL's actual HW state).
Simply return true when we are in tbt mode.

Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Link: https://patch.msgid.link/20260204023247.1560196-1-suraj.kandpal@intel.com