MFC of r310887:

Fix rcc_gpio_modify_bits(). Obviously (1 << 0) is not the same as 0.

Pointy hat to: loos

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

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

Fix off-by-one bugs.

While here, only set the GPIO pin state for output pins.

Pointy hat to: loos
Sponsored by: Rubicon Communications (Netgate)

Add the GPIO driver for the ADI Engineering RCC-VE and RCC-DFF/DFFv2.

This driver allows read the software reset switch state and control the
status LEDs.

The GPIO pins have their direction (input/output) locked down to prevent
possible short circuits.

Note that most people get a reset button that is a hardware reset. The
software reset button is available on boards from Netgate.

Sponsored by: Rubicon Communications (Netgate)