The GEOM KPI in stable/10 requires Giant to be unacquired (a requirement
dropped in r300287). So wrap calling into GEOM in {DROP,PICKUP}_GIANT(),
similar to what as been done prio to r300288. This fixes a "Giant owned"
panic with r318159 in place and INVARIANTS enabled.
Reported by: Oliver Pinter

MFC: r287013 (partial), r294616, r314097 (partial)

- Allow overriding the FDT slicer with a custom slicer.
- Teach the flashmap code about SPI flash.
- Allow different slicers for different flash types to be registered
with geom_flashmap(4) and teach it about MMC for slicing enhanced
user data area partitions. The FDT slicer still is the default for
CFI, NAND and SPI flash on FDT-enabled platforms.
- In addition to a device_t, also pass the name of the GEOM provider
in question to the slicers as a single device may provide more than
one provider.
- Build a geom_flashmap.ko.
- Use MODULE_VERSION() so other modules can depend on geom_flashmap(4).
- Remove redundant/superfluous GEOM routines that either do nothing
or provide/just call default GEOM (slice) functionality.
- Trim/adjust includes

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

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

MFP4 @222836

Add support for partitioning CFI disks from FDT using geom_flashmap.

Sponsored by: DARPA, AFRL

Partial MFP4 of 222836:

Only look for FDT partitions if our potential parent is a DISK device.

Excluding direct recursion on the flashmap geoms was insufficient
because it did not prevent the underlying device from being retrieved if
flashmap geoms were further partitioned.

Reviewed by: imp
Sponsored by: DARPA, AFRL

- Correct signedness for casts;
- Wrap long line while I'm there.

Noticed by: pjd, avg

Use %ju to match uintmax_t usage

Use %j and cast off_t to intmax_t for now to fix build.

Noticed by: bz

Add a new geom class which allows to divide NAND Flash chip
into partitions.

Partitions are created based on data in dts file which are
extracted and interpreted by slicer.

Obtained from: Semihalf
Supported by: FreeBSD Foundation, Juniper Networks