spi: meson-spicc: Use GPIO descriptors

spi: meson-spicc: Use GPIO descriptors

Instead of grabbing GPIOs using the legacy interface and
handling them in the setup callback, just let the core
grab and use the GPIOs using descriptors.

Cc: Neil Armstrong <narmstrong@baylibre.com>
Cc: Sunny Luo <sunny.luo@amlogic.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://lore.kernel.org/r/20191205083915.27650-1-linus.walleij@linaro.org
Signed-off-by: Mark Brown <broonie@kernel.org>