Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC r263052, r263124, r263265, r263267... Enhance loaderdev env var.

Enhance the mechanism that lets you configure the ubldr boot device by
setting the u-boot environment variable loaderdev=. It used to accept only
'disk' or 'net'. Now it allows specification of unit, slice, and partition
as well. In addition to the generic 'disk' it also accepts specific
storage device types such as 'mmc' or 'sata'.

If there isn't a loaderdev env var, the historical behavior is maintained.
It will use the first storage device it finds, or a network device if
no working storage device exists.

99% of the work on this was done by Patrick Kelsey, but I made some
changes, so if anything goes wrong, blame me.

(Indeed, the 3 followup commits fixed things I got wrong on the first.)

MFC r262666: exit with code 0xbadab1 if the u-boot API support is missing.

MFC r262337: Allow the boot device to be choosen by a u-boot env variable.

If a "loaderdev=<device>" env variable is set and the named device
exists, it is used. If the device doesn't exist, fall back to the
historic "probe" loop that prefers disk devices over network devices.

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Update according to the change of struct uboot_devdesc.

Ooops. Back out changes to main.c from r235094.

This change is specific to BeagleBone; I need to figure out how to
generalize this before committing.

Don't call strcmp with a NULL pointer.

In particular, on the AM335x, which comes up with no memory
mapped to low addresses, dereferencing the NULL causes a crash.

Initial loader(8) support for Flattened Device Tree.

o This is disabled by default for now, and can be enabled using WITH_FDT at
build time.

o Tested with ARM and PowerPC.

Reviewed by: imp
Sponsored by: The FreeBSD Foundation

Use loader devices only when they initialized properly.

Let loader(8) for U-Boot use default storage more flexibly.

Obtained from: Semihalf
MFC after: 1 week

Improve style(9) in PowerPC U-Boot support lib.

Improve loader support for U-Boot.

- add new diag commands: devinfo, sysinfo for U-Boot-style details about the system
configuration
- better memory info summary
- style corrections

Obtained from: Semihalf

Move U-Boot compatibility library to WARNS=2 level.

style(9) & style.Makefile(9)

Reviewed by: raj

o Include glue.h
o Support multiple memory regions.

MFp4 (e500):

Add support for U-Boot. This uses the U-Boot API as developed by
Rafal and which is (will be) part of U-Boot 1.3.2 and later.

Credits to: raj@