drm/i915/display: Drop duplicated code in intel_dp_set_infoframes()

No functional changes in here.

Cc: Matt Atwood <matthew.s.atwood@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210418002126.87882-3-jose.souza@intel.com