MFC r260509:
Replace several instances of -1 with appropriate CAM_*_WILDCARD and types.

It was equal before r259397, but for good or bad, not any more for LUNs.

This change fixes at least CAM debugging.
MFC r264274, r264279, r264283, r264296, r264297:
Add support for SCSI UNMAP commands to CTL.

This patch adds support for three new SCSI commands: UNMAP, WRITE SAME(10)
and WRITE SAME(16).  WRITE SAME commands support both normal write mode
and UNMAP flag.  To properly report UNMAP capabilities this patch also adds
support for reporting two new VPD pages: Block limits and Logical Block
Provisioning.

UNMAP support can be enabled per-LUN by adding "-o unmap=on" to `ctladm
create` command line or "option unmap on" to lun sections of /etc/ctl.conf.

At this moment UNMAP supported for ramdisks and device-backed block LUNs.
It was tested to work great with ZFS ZVOLs.  For file-backed LUNs UNMAP
support is unfortunately missing due to absence of respective VFS KPI.

Sponsored by:   iXsystems, Inc
MFC r264406:
Report more readable state "-" for idle CAM scan thread.
MFC r264407:
Join CTL worker threads into one process for convenience.
Report their idle state as "-".
MFC r264834:
Disable UNMAP support for STEC 842 SSDs.

In some unknown cases UNMAP commands make device firmware stuck.
MFC r264880 (by trasz):
Modify CTL iSCSI frontend to properly handle situations where datamove
routine is called multiple times per SCSI task.
MFC r264884:
Make CAM target CTL frontend respect SIM I/O size limitations.

If datamove size is bigger then SIM can handle, or it has more segments
then this code can handle -- split it into several CTIO requests.
MFC r264886:
Remove limits on size of READ/WRITE operations.

Instead of allocating up to 16MB or RAM at once to handle whole I/O,
allocate up to 1MB at a time, but do multiple ctl_datamove() and storage
I/Os if needed.
MFC r265150:
Do not reread SCSI disk VPD pages on every device open.

Instead of rereading VPD pages on every device open, do it only on initial
device probe, and in cases when device reported via UNIT ATTENTIONs that
something has changed.  Capacity is still rereaded on every open because
it is more critical for operation and more probable to change in run time.

On my tests with Intel 530 SSDs on mps(4) HBA this change reduces time
GEOM needs to retaste the device (that includes few open/close cycles)
from ~150ms to ~30ms.
MFC r265159:
Respect MAXIMUM TRANSFER LENGTH field of Block Limits VPD page.

Nobody yet reported disk supporting I/Os less then our MAXPHYS value, but
since we any way have code to read Block Limits VPD page, that is easy.