Removed unneeded tests in dadeletemethodset changing it to return void

Reviewed by:	mav
Approved by:	pjd (mentor)
MFC after:	2 weeks
Added a sysctl (kern.geom.dev.delete_max_sectors) to control the maximum
size of a delete request sent to the providing device performed by g_dev_ioctl.

This allows the kernel and apps via ioctl e.g. newfs -E to request large LBA
deletes which siginificantly improves performance.

Previously this was hard coded to 65536 sectors, the new default is 262144
which doubles the throughput of deletes on commonly available SSD's.

In tests on a Intel 520 120GB FW: 400i disk it improved the delete throughput
from 1.6GB/s to over 2.6GB/s on a full disk delete such as that done via
newfs -E

For some SSD's where delete time is pretty much constant, no matter what
the request, setting this to 0 will provide significantly better throughput
e.g. Samsung 840 240GB FW DXT07B0Q @ 262144 = 79G/s, @ 0 = 2259G/s

Reviewed by:	mav
Approved by:	pjd (mentor)
MFC after:	2 weeks
Added Dataset Management defines to be used by TRIM in cam ata and scsi to
calculate the size of blocks.

Reviewed by:	mav
Approved by:	pjd (mentor)
MFC after:	2 weeks
Added the ability to send ATA identify and Data Set Management (DSM) TRIM
commands to an ATA device attached via a SCSI control.

sys/cam/scsi/scsi_all.c:
        - Added scsi_ata_identify, scsi_ata_trim
          Which use ATA Pass-Through to send commands to the attached disk.

sys/cam/scsi/scsi_all.h:
        - Added defines for all missing ATA Pass-Through commands values.

        - Added scsi_ata_identify, scsi_ata_trim methods used in ATA TRIM
          support.

        - Added scsi_vpd_logical_block_prov structure used when querying for
          the supported sizes UNMAP commands.

        - Added scsi_vpd_block_limits structure used when querying for the
          supported sizes of the UNMAP command.

Reviewed by:	mav
Approved by:	pjd (mentor)
MFC after:	2 weeks
Updated TRIM calculations in cam/ata to be based off ATA_DSM_* defines

Reviewed by:	mav
Approved by:	pjd (mentor)
MFC after:	2 weeks
Refactored scsi_xpt use of device_has_vpd to generic scsi_vpd_supported_page
so its available for use in generic scsi code.

This is a pre-requirement for using VPD queries to determine available SCSI
delete methods within scsi_da.

Reviewed by:	mav
Approved by:	pjd (mentor)
MFC after:	2 weeks
Added available delete methods discovery during device probe, including the
maximum sizes for said methods, which are used when processing BIO_DELETE
requests. This includes updating UNMAP support discovery to be based on
SBC-3 T10/1799-D Revision 31 specification.

Added ATA TRIM support to cam scsi devices via ATA Pass-Through(16)

sys/cam/scsi/scsi_da.c:
        - Added ATA Data Set Management TRIM support via ATA Pass-Through(16)
          as a delete_method

        - Added four new probe states used to identity available methods and their
          limits for the processing of BIO_DELETE commands via both UNMAP and the
          new ATA TRIM commands.

        - Renamed Probe states to better indicate their use

        - Added delete method descriptions used when informing user of issues.

        - Added automatic calculation of the optimum delete mode based on which
          method presents the largest maximum request size as this is most likely
          to result in the best performance.

        - Added WRITE SAME max block limits

        - Updated UNMAP range generation to mirror that used by ATA TRIM, this
          optimises the generation of ranges and fixes a potential overflow
          issue in the count when combining multiple BIO_DELETE requests

        - Added output of warnings about short deletes. This should only ever
          be triggered on devices that fail to correctly advertise their supported
          delete modes / max sizes.

        - Fixed WS16 requests being incorrectly limited to 65535 in length.

Reviewed by:	mav
Approved by:	pjd (mentor)
MFC after:	2 weeks