staging: lustre: obdecho: remove unneeded null test before free

Kfree can cope with a null argument, so drop null tests.

The semantic patch that makes this change is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@ expression ptr; @@

- if (ptr != NULL)
  kfree(ptr);
// </smpl>
Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/obdecho/echo_client.c

@@ -1737,9 +1737,7 @@ static int echo_client_prep_commit(const struct lu_env *env,
 	}
 
 out:
-	if (lnb)
 	kfree(lnb);
-	if (rnb)
 	kfree(rnb);
 	return ret;
 }