spi: img-spfi: Convert to use GPIO descriptors

spi: img-spfi: Convert to use GPIO descriptors

This converts the IMG SPFI SPI driver to use GPIO descriptors
as obtained from the core instead of GPIO numbers.

The driver was already relying on the core code to look up
the GPIO numbers from the device tree and allocate memory for
storing state etc. By moving to use descriptors handled by
the core we can delete the setup/cleanup functions and
the device state handler that were only dealing with this.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Cc: Ionela Voinescu <ionela.voinescu@imgtec.com>
Cc: Sifan Naeem <sifan.naeem@imgtec.com>
Link: https://lore.kernel.org/r/20200625201422.208640-1-linus.walleij@linaro.org
Signed-off-by: Mark Brown <broonie@kernel.org>