drm/i915/tgl: allow DVI/HDMI on port A

Tiger Lake supports HDMI on port A. For other platforms we ignore what
the VBT says regarding HDMI to workaround broken VBTs, see
commit 2ba7d7e0 ("drm/i915/bios: ignore HDMI on port A"). Make this
apply gen12+ so they inherit the TGL behavior.

Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191113021935.41547-1-lucas.demarchi@intel.com