IB/usnic: delete unneeded IS_ERR test

kzalloc doesn't return ERR_PTR, so there is no need to test for it.

The semantic match that finds this problem is as follows:
(http://coccinelle.lip6.fr/

)

// <smpl>
@@
expression x,e;
@@

* x = kzalloc(...)
... when != x = e
* IS_ERR_OR_NULL(x)
// </smpl>

Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Reviewed-by: Dave Goodell <dgoodell@cisco.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>