cxgbe(4): Changes to the CPL-handler registration mechanism and code

cxgbe(4): Changes to the CPL-handler registration mechanism and code
related to "shared" CPLs.

a) Combine t4_set_tcb_field and t4_set_tcb_field_rpl into a single
function.  Allow callers to direct the response to any iq.  Tidy up
set_ulp_mode_iscsi while there to use names from t4_tcb.h instead of
magic constants.

b) Remove all CPL handler tables from struct adapter.  This reduces its
size by around 2KB.  All handlers are now registered at MOD_LOAD instead
of attach or some kind of initialization/activation.  The registration
functions do not need an adapter parameter any more.

c) Add per-iq handlers to deal with CPLs whose destination cannot be
determined solely from the opcode.  There are 2 such CPLs in use right
now: SET_TCB_RPL and L2T_WRITE_RPL.  The base driver continues to send
filter and L2T_WRITEs over the mgmtq and solicits the reply on fwq.
t4_tom (including the DDP code) now uses the port's ctrlq to send
L2T_WRITEs and SET_TCB_FIELDs and solicits the reply on an ofld_rxq.
fwq and ofld_rxq have different handlers that know what kind of tid to
expect in the reply.  Update t4_write_l2e and callers to to support any
wrq/iq combination.

Approved by:	re@ (kib@)
Sponsored by:	Chelsio Communications