[SCSI] mpt2sas: New feature - Fast Load Support

[SCSI] mpt2sas: New feature - Fast Load Support

New feature Fast Load Support.

(1)Asynchronous SCSI scanning: This will allow the drivers to scan
for devices in parallel while other device drivers are loading at
the same time. This will improve the amount of time it takes for the
OS to load.

(2) Reporting Devices while port enable is active: This feature will
allow devices to be reported to OS immediately while port enable is
active. The previous implementation waits for port enable to complete,
and then report devices. This feature is only enabled on IT firmware
configurations when there are no boot device configured in BIOS Configuration
Utility, else the driver will wait till port enable completes reporting
devices. For IR firmware, this feature is turned off. This feature is to
address large SAS topologies (>100 drives) when the boot OS is using onboard
SATA device, in other words, the boot devices is not
connected to our controller.

(3) Scanning for devices after diagnostic reset completes: A new routine
_scsih_scan_start is added. This will scan the expander pages, IR pages,
and sas device pages, then reporting new devices to SCSI Mid layer. It
seems the driver is not supporting adding devices while diagnostic reset
is active. Apparently this is due to the sanity checks on
ioc->shost_recovery flag throughout the context of kernel work thread FIFO,
and the mpt2sas_fw_work.

Signed-off-by: Nagalakshmi Nandigama <nagalakshmi.nandigama@lsi.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>