Fix a case in ndling ATA_PASSTHROUGH commands that have an unaligned buffer.
This impacts some home-rolled SMART tools.

Reviewed by:	jimharris
Obtained from:	Netflix
MFC after:	2 days
In rare cases, a SATA drive can stop responding to commands and trigger a
reset device task request from the driver.  If the drive fails to respond
with a signature FIS, the driver would previously get into an endless retry
loop, stalling all I/O to the drive and keeping user processes stranded.
Instead, fail the i/o and invalidate the device if the task management
command times out.  This is controllable with the sysctl and tunable
hw.isci.fail_on_task_timeout
dev.isci.0.fail_on_task_timeout

The default for these is 1.

Reviewed by:	jimharris
Obtained from:	Netflix, Inc.
MFC after:	2 days