drm/i915/tc: Wait for IOM/FW PHY initialization of legacy TC ports

During boot-up/system resume, the TC PHY on legacy ports will be
initialized by the IOM/TCSS firmware regardless of a sink being
connected or not (as opposed to DP-alt/TBT ports, which the FW only
inits once a sink is connected).

Wait for the above initialization to complete during HW readout, so that
connecting the PHY later will already see the expected PHY ready state.

Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230316131724.359612-6-imre.deak@intel.com