Merge thorpej-cfargs2.

Merge thorpej-cfargs branch:

Simplify and make extensible the config_search() / config_found() /
config_attach() interfaces: rather than having different variants for
which arguments you want pass a

Merge thorpej-cfargs branch:

Simplify and make extensible the config_search() / config_found() /
config_attach() interfaces: rather than having different variants for
which arguments you want pass along, just have a single call that
takes a variadic list of tag-value arguments.

Adjust all call sites:
- Simplify wherever possible; don't pass along arguments that aren't
actually needed.
- Don't be explicit about what interface attribute is attaching if
the device only has one. (More simplification.)
- Add a config_probe() function to be used in indirect configuiration
situations, making is visibly easier to see when indirect config is
in play, and allowing for future change in semantics. (As of now,
this is just a wrapper around config_match(), but that is an
implementation detail.)

Remove unnecessary or redundant interface attributes where they're not
needed.

There are currently 5 "cfargs" defined:
- CFARG_SUBMATCH (submatch function for direct config)
- CFARG_SEARCH (search function for indirect config)
- CFARG_IATTR (interface attribte)
- CFARG_LOCATORS (locators array)
- CFARG_DEVHANDLE (devhandle_t - wraps OFW, ACPI, etc. handles)

...and a sentinel value CFARG_EOL.

Add some extra sanity checking to ensure that interface attributes
aren't ambiguous.

Use CFARG_DEVHANDLE in MI FDT, OFW, and ACPI code, and macppc and shark
ports to associate those device handles with device_t instance. This
will trickle trough to more places over time (need back-end for pre-OFW
Sun OBP; any others?).

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Update for proplib(3) API changes.

Cleanup i2c bus acquire / release, centralizing all of the logic into
iic_acquire_bus() / iic_release_bus(). "acquire" and "release" hooks
no longer need to be provided by back-end controller driver

Cleanup i2c bus acquire / release, centralizing all of the logic into
iic_acquire_bus() / iic_release_bus(). "acquire" and "release" hooks
no longer need to be provided by back-end controller drivers (only if
they need special handling, e.g. powering on the i2c controller).
This results in the removal of a bunch of rendundant code from each
back-end controller driver.

Assert that we are not in hard interrupt context in iic_acquire_bus(),
iic_exec(), and iic_release_bus().

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Use PRIx64 printf format to make the 32bit version compile.

- map registers ourselves, no more schizo hackery
- remove some leftover debug code
- print address when attaching
- actually lock/unlock in acquire_bus()/release_bus()
should be ready for general co

- map registers ourselves, no more schizo hackery
- remove some leftover debug code
- print address when attaching
- actually lock/unlock in acquire_bus()/release_bus()
should be ready for general consumption now

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support for jbus-i2c found in US-IIIi machines
this needs help from schizo to access its registers, which is suboptimal and
should go away. So, for now this is for documentation purposes only.