drm/i915/display: Drop FIXME about turn off infoframes

intel_dp_set_infoframes() call in intel_ddi_post_disable_dp() will
take care to disable all enabled infoframes.

Cc: Ville Syrjälä <ville.syrjala@linux.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/20210514232247.144542-4-jose.souza@intel.com