Reduce per-LUN memory usage from 18MB to 1.8MB.

CTL never had use for CA support code since SPI has gone, and there is no
even frontends supporting that.  But it still was reserving 256 bytes of
memory per LUN per every possible initiator on every possible port.

Wrap unused code with ifdef's in case somebody even need it.

MFC after:	2 weeks

(cherry picked from commit b324b7bdb5795179d4a19f90251bb9e4cf9029e1)
Increase maximal number of SCSI ports in CTL from 32 to 128.

After I gave each iSCSI target its own port, the old limit appeared to be
not so big.  This change almost proportionally increases per-LUN memory
use, but it is still three times better then it was before r268807.

MFC after:	2 weeks

(cherry picked from commit c253b272de56534871290ca33584d683c8cfa16d)