drm/i915/display: combine DP audio compute config steps

Combine all DP audio configs into a single function

Signed-off-by: Vinod Govindapillai <vinod.govindapillai@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230818111950.128992-3-vinod.govindapillai@intel.com