drm/i915/xe2lpd: Read pin assignment from IOM

Starting from display version 20, we need to read the pin assignment
from the IOM TCSS_DDI_STATUS register instead of reading it from the
FIA.

We use the pin assignment to decide the maximum lane count.  So, to
support this change, add a new lnl_tc_port_get_max_lane_count() function
that reads from the TCSS_DDI_STATUS register and decides the maximum
lane count based on that.

BSpec: 69594
Cc: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230919192128.2045154-14-lucas.demarchi@intel.com