MFC r349883: owc_gpiobus: small formatting cleanup

MFC r349428,r349433: owc_gpiobus: clean / fix up the driver module things

"fdt" is removed from the driver module name as the driver does not
require FDT and can work very well on hints based systems.

A module dependency is added for gpiobus. Without that owc cannot
resolve symbols in gpiobus if both are loaded as kernel modules.

Finally, a driver module module version is added.

MFC r321686:

Add inline functions to convert between sbintime_t and decimal time units.
Use them in some existing code that is vulnerable to roundoff errors.

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

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

Don't repeat the the word 'the'

(one manual change to fix grammar)

Confirmed With: db
Approved by: secteam (not really, but this is a comment typo fix)

dev/ow: Tag an unreachable switch default.

Coverity reports an uninitialized "dir" in case the switch defaults
without hitting any case. Respect the original intent and quell the
false positive with the relatively new __unreachable() builtin.

CID: 1331566

Cleanup unnecessary semicolons from the kernel.

Found with devel/coccinelle.

Simply to appease gcc's warnings.

New 1-Wire bus implementation. 1-Wire controller is abstracted, though
only gpiobus configured via FDT is supported. Bus enumeration is
supported. Devices are created for each device found. 1-Wire
temperature controllers are supported, but other drivers could be
written. Temperatures are polled and reported via a sysctl. Errors
are reported via sysctl counters. Mis-wired bus detection is included
for more trouble shooting. See ow(4), owc(4) and ow_temp(4) for
details of what's supported and known issues.

This has been tested on Raspberry Pi-B, Pi2 and Beagle Bone Black
with up to 7 devices.

Differential Revision: https://reviews.freebsd.org/D2956
Relnotes: yes
MFC after: 2 weeks
Reviewed by: loos@ (with many insightful comments)