libsa: Remove redundant sys/cdefs.h

Sponsored by: Netflix

Remove $FreeBSD$: one-line .c pattern

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\n/

stand: Create common gen_setcurrdev and replace code

Replace 4 identical copies of *_setcurrdev with gen_setcurrdev to avoid
having to create a 5th copy. uboot_setcurrdev is actually different and
needs to remain separate (even though it's quite similar).

Sponsored by: Netflix
Reviewed by: fuz@fuz.su, kevans
Differential Revision: https://reviews.freebsd.org/D38003

stand/i386: Move to using common devparse()

We no longer need to have to hand-code this for each boot loader since
devparse() handles them all with dv_parsedev().

Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D37341

stand: Change zfs_parsedev() API

Change the first argument to zfs_parsedev() to be a pointer to a struct
devdesc *. This now gets filled in with a malloc'd structure that's
returned to the caller that the caller is repsonsible for freeing. Most
nplaces in the tree passed in a malloc'd pointer anyway, and this moves
knowledge of zfs_devdesc more firmly into the zfs.c code.

Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D37336

stand: Change disk_parsedev() API

Change the first argument to disk_parsedev() to be a pointer to a struct
devdesc *. This now gets filled in with a malloc'd structure that's
returned to the caller that the caller is repsonsible for freeing. Most
places in the tree passed in a malloc'd pointer anyway, and this moves
knowledge of disk_devdesc more firmly into the disk.[ch] code.

Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D37335

stand: i386_fmtdev can be reduced to devformat

devformat produces the same output as i386_fmtdev, so just use it to
reduce on the dependencies.

Sponsored by: Netflix
Reviewed by: tsoome
Differential Revision: https://reviews.freebsd.org/D35927

loader: implement mount/unmount rootfs

We want to keep our root file system open to preserve bcache segment
between file accesses, thus reducing physical disk IO.

Reviewed by: imp, allanjude, kevans (previous version)
Differential Revision: https://reviews.freebsd.org/D30848
MFC after: 1 month

i386_parsedev() needs to support fd devices

MFC after: 2 weeks

Stop using ../zfs/libzfs.h but instead use libzfs.h.

While ../zfs/libzfs.h mostly works, there are a few situations where
it does not. Eliminate the problem by using plain libzfs.h, like we do
for ufs support. This fixes the weird cases, and is easier to
understand. It also follows the general style convetion of avoiding
../ in #includes.

Remove d_type from devdesc. It's not needed as we can fetch it from
d_dev->dv_type when we need it.

Use the actual struct devdesc at the start of all *_devdesc structs

The current system is fragile and requires very careful layout of all
*_devdesc structures. It also makes it hard to change the base
devdesc. Take a page from CAM and put the 'header' in all the derived
classes and adjust the code to match.

For OFW, move the iHandle h_handle out of a slot conflicting with
d_opendata. Due to quirks in the alignment rules, this worked.
However changing the code to use d_opendata storage now that it's a
pointer is hard, so just have a separate field for it.

All other cleanups were to make the *_devdesc structures match where
they'd taken some liberties that were none-the-less compatible enough
to work.

Move sys/boot to stand. Fix all references to new location

Sponsored by: Netflix