IB/rxe: clean skb queue directly

When resp is in error state, the queued SKBs will not be handled.
The function get_req cleans up the skb queue directly.

CC: Srinivas Eeda <srinivas.eeda@oracle.com>
CC: Junxiao Bi <junxiao.bi@oracle.com>
Signed-off-by: Zhu Yanjun <yanjun.zhu@oracle.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>