IB/nes: Fix incorrect type in assignment

Fix mismatch between types, wqe_words are in le32 format, while opcode
in CPU format.

The following sparse warnings are helped to find it:

drivers/infiniband/hw/nes/nes_hw.c:3058:24: warning: incorrect type in assignment (different base types)
drivers/infiniband/hw/nes/nes_hw.c:3058:24:    expected unsigned int [unsigned] [assigned] [usertype] opcode
drivers/infiniband/hw/nes/nes_hw.c:3058:24:    got restricted __le32 <noident>

CC: Faisal Latif <faisal.latif@intel.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>