drm/i915/dp: Extract intel_dp_has_audio()

Declutter intel_dp_compute_config() a bit by moving the
has_audio computation into a helper. HDMI already does the same thing.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220322120015.28074-4-ville.syrjala@linux.intel.com


Reviewed-by: Uma Shankar <uma.shankar@intel.com>