Fix the i2c bus speed divisors for TI OMAP4 and AM335x.

For OMAP4, the old values for 1MHz gave a bus frequency of about 890KHz.
The new numbers hit 1MHz exactly.

For AM335x the prescaler values are adjusted to give a 24MHz clock for
all 3 standard speeds, as the manual recommends (as near as we can tell,
there are errors and typos apparent in the document).  Also, 1MHz speed
is added, and has been tested successfully on a BeagleboneWhite board.

PR:		195009
Collapse three contiguous comment blocks into one. Remove historical
note about wrong assumptions 20 years ago. Use proper casing.

Sponsored by:	Nginx, Inc.
Re-work non-persistent filesystem detection as it was not possible to
detect /dev/md backed mfs filesystems that way.

Differential Revision:	https://reviews.freebsd.org/D1163
Approved by:	ian
Add Virtio MMIO bus driver.

Sponsored by:	DARPA, AFRL
Add Altera Parallel IO (PIO) device driver.

Sponsored by:	DARPA, AFRL
Missed a terminating ';'.

X-MFC-with:	r273009
Implement the historic DIOCGDINFO ioctl for gpart on BSD
partitions. Several utilities still use this interface and require
additional information since gpart was activated than before. This
allows fsck of a UFS partition without having to specify it is UFS,
per historic behavior.
Acutally, replaces NO_INCS with WITHOUT_INCLUDES and make
WITHOUT_TOOLCHAIN imply it instead.

Sponsored by: Netflix
Fix typo pointed out by avg@ and Joerg Sonnenberger. Add a clarifying
sentence too.

Sponsored by: Netflix
LIB32 is supported for powerpc64 too. Make the note more general about
64-bit processors.

Sponsored by: Netflix
Document WITHOUT_USB_EXAMPLES and WITHOUT_TESTS_SUPPORT

Sponsored by: Netflix
opt_global.h is never needed in SRCS lists.

Sponsored by: Netflix
No need to list opt_global.h. No need to force ALTQ here, since that's
not the normal default for the system and nothing else forces it on.

Sponsored by: Netflix
opt_global.h is included automatically in the build. No need to
explicitly include it in these places.

Sponsored by: Netflix
These delays aren't needed. Elimate them. They should be on the order
of a few cycles at most, not 10us. They make it impossible to
implement half-duplex protocols that are faster than about 1KHz.

Sponsored by: Netflix
Moves all the duplicate code to a single function.

Verify for invalid modes and unwanted flags before pass the new flags to
driver.
Make gpio_default_map_gpios() static.  No functional changes.
Upgrade libxo to 0.1.6.

Summary of changes:
1.  Coverity defect fixes

Obtained from:  https://github.com/Juniper/libxo/releases/tag/0.1.6
Allow tuning zfs_max_recordsize via loader tunable.  Tuning is NOT
recommended.

Requested by:	Slawa Olhovchenkov <slw zxy spb ru>
MFC after:	2 weeks
Add a tunable for spa_slop_shift which controls how much space we
would reserve by default.  Tuning is not recommended.

MFC after:	2 weeks