RDMA/nes: Fix two sparse warnings

Simple changes to fix warnings:

      CHECK   drivers/infiniband/hw/nes/nes_verbs.c
    nes_verbs.c:1944:45: warning: Using plain integer as NULL pointer
    nes_verbs.c:1944:48: warning: Using plain integer as NULL pointer
      CHECK   drivers/infiniband/hw/nes/nes_cm.c
    nes_cm.c:2645:43: warning: mixing different enum types
    nes_cm.c:2645:43:     int enum iw_cm_event_type  versus
    nes_cm.c:2645:43:     int enum iw_cm_event_status

Signed-off-by: Or Gerlitz <ogerlitz@voltaire.com>
Acked-by: Chien Tung <chien.tin.tung@intel.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>