dt-bindings: pinctrl: Document optional BCM7211 wake-up interrupts

BCM7211 supports wake-up interrupts in the form of optional interrupt
lines, one per bank, plus the "all banks" interrupt line.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20200531001101.24945-3-f.fainelli@gmail.com


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>