Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error
prone - task.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

Found with devel/coccinelle.

Make it clearer what each one means in the comments that define them.

IIC_BUSBSY was used in many places to mean two different things, either
"someone else has reserved the bus so you have to wait until they're done"
or "the signal level on the bus was not in the state I expected before/after
issuing some command".

Now IIC_BUSERR is used consistantly to refer to protocol/signaling errors,
and IIC_BUSBSY refers to ownership/reservation of the bus.

input buf is const

Reviewed by:	imp, current@
Approved by:	jhb (mentor)

  of having duplicate versions in each bus attachment.
- Add a DRIVER_MODULE() instance so that the iicbus(4) driver will
  actually attach to pcf(4) driver instances.
- Fix compile of envctrl.c.

Pointy hat:	jhb (3)

- Just grab Giant in the ixp425_iic(4) driver since this driver uses
  a shared address/data register window pair to access the actual
  I2C registers.  None of the other ixp425 drivers lock access to these
  shared address/data registers yet and that would need to be done before
  this could use any meaningful locking.
- Add locking to the interrupt handler and 'iicbus_reset' methods of the
  at91_twi(4) driver.
- Add locking to the pcf(4) driver.  Other pcf(4) fixes include:
  - Don't needlessly zero the softc.
  - Use bus_foo rather than bus_space_foo and remove bus space tag and
    handle from softc.
- The lpbb(4) driver just grabs Giant for now.  This will be refined later
  when ppbus(4) is locked.
- As was done with smbus earlier, move the DRIVER_MODULE() lines to match
  the bus driver (either iicbus or iicbb) to the bridge driver into the
  bridge drivers.

Tested by:	sam (arm/ixp425)

my Elektor card. Note that the hints are necessary to specify the
IO base of the pcf chip. This enables to check the IO base when the
probe routine is called during ISA enumeration.

The interrupt driven code is mixed with polled mode, which is wrong
and produces supposed spurious interrupts at each access. I still have
to work on it.

This splits the driver into a bus-independant backend, plus bus-specific
frontends.  The old pcf(4) (i386/ISA) frontend is now in pcf_isa.c, the
frontend in envctrl.c is for sparc64/Ebus2 (Sun device name: SUNW,envctrl
from Sun E450 machines).  More frontends are expected to appear in future.

This is not yet ready for public consumption, but it basically works.
Nicolas will bring over his ISA-specific fixes soon.

Reviewed by:	nsouch

Only cy, bs and wd in the tree still use it.  I have a replacement for
cy that I need to test on ISA and PCI cards.  bs and wd are pc98 only
drivers that appear to no longer be necessary.  I'll be removing them
when I hear back from the pc98 people.

an int.