target: Move task tag into struct se_cmd + support 64-bit tags

Simplify target core and target drivers by storing the task tag
a.k.a. command identifier inside struct se_cmd.

For several transports (e.g. SRP) tags are 64 bits wide.
Hence add support for 64-bit tags.

(Fix core_tmr_abort_task conversion spec warnings - nab)
(Fix up usb-gadget to use 16-bit tags - HCH + bart)

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Andy Grover <agrover@redhat.com>
Cc: Sagi Grimberg <sagig@mellanox.com>
Cc: <qla2xxx-upstream@qlogic.com>
Cc: Felipe Balbi <balbi@ti.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

diff --cc Documentation/target/tcm_mod_builder.py
Simple merge

diff --cc drivers/infiniband/ulp/srpt/ib_srpt.c
Simple merge

diff --cc drivers/infiniband/ulp/srpt/ib_srpt.h
Simple merge

diff --cc drivers/scsi/qla2xxx/qla_target.c
Simple merge

diff --cc drivers/scsi/qla2xxx/qla_target.h
Simple merge

diff --cc drivers/scsi/qla2xxx/tcm_qla2xxx.c
Simple merge

diff --cc drivers/target/iscsi/iscsi_target.c
Simple merge

diff --cc drivers/target/iscsi/iscsi_target_configfs.c
Simple merge

diff --cc drivers/target/loopback/tcm_loop.c
Simple merge

diff --cc drivers/target/sbp/sbp_target.c
Simple merge

diff --cc drivers/target/target_core_configfs.c
Simple merge

diff --cc drivers/target/target_core_tmr.c
Simple merge

diff --cc drivers/target/target_core_transport.c
Simple merge

diff --cc drivers/target/target_core_xcopy.c
Simple merge

diff --cc drivers/target/tcm_fc/tcm_fc.h
Simple merge

diff --cc drivers/target/tcm_fc/tfc_cmd.c
Simple merge

diff --cc drivers/target/tcm_fc/tfc_conf.c
Simple merge

diff --cc drivers/usb/gadget/legacy/tcm_usb_gadget.c
Simple merge

diff --cc drivers/vhost/scsi.c
Simple merge

diff --cc drivers/xen/xen-scsiback.c
Simple merge

diff --cc include/target/target_core_base.h
Simple merge

diff --cc include/target/target_core_fabric.h
Simple merge