intel_bios_is_port_hpd_inverted() is only used on bxt/glk on
which we always have encoder->devdata available. So consult
that instead of digging around in vbt.ports[].

And rename the function to match the common pattern.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230208015508.24824-6-ville.syrjala@linux.intel.comReviewed-by: Jani Nikula <jani.nikula@intel.com>