MFC r256151:

Add driver-assisted striping for upcoming Intel NVMe controllers that can
benefit from it.

Sponsored by:	Intel
MFC r256152:

Extend some 32-bit fields and variables to 64-bit to prevent overflow
when calculating data in nvmecontrol perftest.

Sponsored by:	Intel
MFC r256153:

Do not enable temperature threshold as an asynchronous event notification
on NVMe controllers that do not support it.

Sponsored by:	Intel
MFC r256154:

Log and then disable asynchronous notification of persistent events after
they occur.

This prevents repeated notifications of the same event.

Status of these events may be viewed at any time by viewing the
SMART/Health Info Page using nvmecontrol, whether or not asynchronous
events notifications for those events are enabled.  This log page can
be viewed using:

    nvmecontrol logpage -p 2 <ctrlr id>

Future enhancements may re-enable these notifications on a periodic basis
so that if the notified condition persists, it will continue to be logged.

Sponsored by:	Intel
MFC r256155:

Do not leak resources during attach if nvme_ctrlr_construct() or the initial
controller resets fail.

Sponsored by:	Intel