This change adds documentation for xfrm4_gc_thresh and xfrm6_gc_thresh
based on the comments in commit eeb1b733 ("xfrm: Increase the garbage
collector threshold").
Signed-off-by: NAlexander Duyck <alexander.h.duyck@redhat.com>
Signed-off-by: NSteffen Klassert <steffen.klassert@secunet.com>