nfs: remove empty if statement from nfs3_prepare_get_acl

Remove empty if statement from nfs3_prepare_get_acl and update comment to
follow the one from the referred fs/posix_acl.c:get_acl().

No functional change intended.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Uros Bizjak <[e-mail]>
Cc: Trond Myklebust <[e-mail]>
Cc: Anna Schumaker <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

fs/nfs/nfs3acl.c

···
 {
 	struct posix_acl *sentinel = uncached_acl_sentinel(current);
 
-	if (cmpxchg(p, ACL_NOT_CACHED, sentinel) != ACL_NOT_CACHED) {
-		/* Not the first reader or sentinel already in place. */
-	}
+	/* If the ACL isn't being read yet, set our sentinel. */
+	cmpxchg(p, ACL_NOT_CACHED, sentinel);
 }
 
 static void nfs3_complete_get_acl(struct posix_acl **p, struct posix_acl *acl)