drm/i915/mtl: Add TC port lockdep assert to AUX power well enabling

Similarly to earlier platforms, assert in the MTL AUX power well
enabling handler for TC AUX CH power wells that the TC port using the
AUX CH is locked.

Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230830140421.2031111-2-imre.deak@intel.com