drm/i915: Extract intel_hdmi_has_audio()

drm/i915: Extract intel_hdmi_has_audio()

Pull the "do we want to enable audio?" computation into a small helper
to make intel_hdmi_compute_config() less messy. Will make it easier to
add more checks for this later (eg. we should actually be checking
at the hblank is long enough for audio transmission).

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200904115354.25336-16-ville.syrjala@linux.intel.com
Reviewed-by: Lyude Paul <lyude@redhat.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>