drm/i915/tc: Assume a TC port is legacy if VBT says the port has HDMI

Since an HDMI output can only be enabled in legacy mode on TC ports,
assume that VBT is wrong and the port is legacy if VBT says the port is
non-legacy and has HDMI. If VBT says to enable DP as well leave the
non-legacy flag enabled, relying on the flag getting fixed up based on
the HPD status during sink detection.

v2: Fix the legacy port flag only if DP is not enabled.

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230321220101.983366-1-imre.deak@intel.com