staging: wfx: Get descriptors for GPIOs

staging: wfx: Get descriptors for GPIOs

The code has the functionality to insert the GPIO lines using
the global GPIO numbers through module parameters.

As we are clearly deprecating the use of global GPIO numbers
look up the GPIO descriptors from the device instead. This
usually falls back to device hardware descriptions using e.g.
device tree or ACPI. This device clearly supports device
tree when used over SPI for example.

For example, this can be supplied in the device tree like so:

  wfx@0x01 {
      compatible = "silabs,wf200";
      reset-gpios = <&gpio0 1>;
      wakeup-gpios = <&gpio0 2>;
  };

Cc: Jérôme Pouiller <jerome.pouiller@silabs.com>
Reviewed-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20200703130756.514868-1-linus.walleij@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>