Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

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

MFC: r234281

- Try to bring these files closer to style(9).
- Use DEVMETHOD_END.
- Use NULL instead of 0 for pointers.

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Tweak the disclaimer section of the license to match COPYRIGHT, for
better or worse. Ok'd by folks that have additional copyrights to the
files in cases where there's joint authorship.

Provide hooks into the GPIO lines and the ability to set/clear
interrupts from them. This should be more generalized, but is
sufficient for now.

Submitted by: Hans Petter Selasky

MFp4:
Introduce framework to configure the multiplexed pins on boot.

Since the USART supprots RS-485 multidrop mode, it allows the
TX pins to float. However, for RS-232 operations, we don't
want these pins to float. Instead, they should be pulled up
to avoid mismatches. Linux does something similar when it
configures the TX lines. This implies that we also allow the
RX lines to float rather than be in the state they are left in
by the boot loader. Since they are input pins, I think that
this is the right thing to do.

Plus minor for our board.

Add support for configuring pins to be one of {GPIO, PERIPHERAL A or
PERIPHERAL B}, as well as direction of GPIO pin. Add defines for all
the pins.