qla2xxx: Enable Target counters in DebugFS.

Following counters are added in target mode to help debugging efforts.

Target Counters

qla_core_sbt_cmd = 0
qla_core_ret_sta_ctio = 0
qla_core_ret_ctio = 0
core_qla_que_buf = 0
core_qla_snd_status = 0
core_qla_free_cmd = 0
num alloc iocb failed = 0
num term exchange sent = 0
num Q full sent = 0

Signed-off-by: Himanshu Madhani <himanshu.madhani@qlogic.com>
Signed-off-by: Giridhar Malavali <giridhar.malavali@qlogic.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>