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 r249449:

Fix undefined behaviour in several gpio_pin_setflags() routines (under
sys/arm and sys/mips), squelching the clang 3.3 warnings about this.

Noticed by: tinderbox and many irate spectators
Submitted by: Luiz Otavio O Souza <loos.br@gmail.com>
PR: kern/177759

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

Approved by: re (implicit)

Fix GPIO_MAXPINS calculation for the AR71xx, AR724x, AR913x SoC.

Submitted by: Luiz Otavio O Souza <loos.br@gmail.com>

- Fix values of CS1_EN and CS2_EN flags
- Unbreak kernel build by fixing naming convention of
GPIO_FUNC flags

Spotted by: Luiz Otavio O Souza, Andrew Thompson

Add AR71XX GPIO bus driver.