spi: bcm2835aux: Convert to use GPIO descriptors

spi: bcm2835aux: Convert to use GPIO descriptors

This one is pretty straight forward to switch over, the driver
already relies on inspecting cs_gpio just check cs_gpiod instead
and stop the special handling of requesting the GPIO and stuff
the core will take care of.

Cc: Lukas Wunner <lukas@wunner.de>
Cc: Martin Sperl <kernel@martin.sperl.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20220201012956.563272-1-linus.walleij@linaro.org
Signed-off-by: Mark Brown <broonie@kernel.org>