RDMA/cxgb3: Shrink .text with compile-time init of handlers arrays

Using compile-time designated initializers for the handler arrays
instead of open-coding the initialization in iwch_cm_init() is (IMHO)
cleaner, and leads to substantially smaller code: on my x86-64 build,
bloat-o-meter shows:

add/remove: 0/1 grow/shrink: 4/3 up/down: 4/-1682 (-1678)
function                                     old     new   delta
tx_ack                                       167     168      +1
state_set                                     55      56      +1
start_ep_timer                                99     100      +1
pass_establish                               177     178      +1
act_open_req_arp_failure                      39      38      -1
sched                                         84      82      -2
iwch_cm_init                                 442      91    -351
work_handlers                               1328       -   -1328

Signed-off-by: Roland Dreier <rolandd@cisco.com>