bcm2835_spi: guard against too large clock divider and clamp if necessary

Remove unnecessary gotos and label. Same code before and after.

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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fdtbus_intr_establish -> fdtbus_intr_establish_xname

Rename of_match_compat_data() to of_compatible_match(). Similarly,
rename of_search_compatible() to of_compatible_lookup().

Standardize on of_compatible_match() for driver matching, and adapt
all c

Rename of_match_compat_data() to of_compatible_match(). Similarly,
rename of_search_compatible() to of_compatible_lookup().

Standardize on of_compatible_match() for driver matching, and adapt
all call sites.

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Use mutex for lwp/interrupt coordination. using splX() simply does not work
on multiprocessor systems.

fixes PR kern/55506

ensure spibus_attach_args is zero'ed

FDTise RapberryPI support. Thanks for jmcneill for a lot of help with this.

The kernel image that the RPI firmware boots is now netbsd.img in the
kernel build directory.

XXX fdtbus_get_reg needs re

FDTise RapberryPI support. Thanks for jmcneill for a lot of help with this.

The kernel image that the RPI firmware boots is now netbsd.img in the
kernel build directory.

XXX fdtbus_get_reg needs reworking

show more ...

When expanding an inline function make sure you get the argument order
correct!

Now there's no functional change to expanding bcm2835_intr_establish

Expand the bcm2835_intr_establish inline.

No functional change.

IPL_BIO -> IPL_VM

No functional change. No code change... It's the same thing!

Add driver for BCM2835 SPI0 controller.