spi: dw: Convert to use CS GPIO descriptors

This converts the DesignWare (dw) SPI master driver to
use GPIO descriptors for chip select handling.

This driver has a duplicate DT parser in addition to the
one in the core, sets up the line as non-asserted and
relies on the core to drive the GPIOs.

It is a pretty straight-forward conversion.

Cc: Talel Shenhar <talel@amazon.com>
Cc: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Linuxarm <linuxarm@huawei.com>
Tested-by: Jay Fang <f.fangjian@huawei.com>
Reviewed-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-dw-mmio.c

@@ -18,7 +18,6 @@
 #include <linux/mfd/syscon.h>
 #include <linux/module.h>
 #include <linux/of.h>
-#include <linux/of_gpio.h>
 #include <linux/of_platform.h>
 #include <linux/acpi.h>
 #include <linux/property.h>
@@ -185,27 +184,6 @@ static int dw_spi_mmio_probe(struct platform_device *pdev)
 
 	dws->num_cs = num_cs;
 
-	if (pdev->dev.of_node) {
-		int i;
-
-		for (i = 0; i < dws->num_cs; i++) {
-			int cs_gpio = of_get_named_gpio(pdev->dev.of_node,
-					"cs-gpios", i);
-
-			if (cs_gpio == -EPROBE_DEFER) {
-				ret = cs_gpio;
-				goto out;
-			}
-
-			if (gpio_is_valid(cs_gpio)) {
-				ret = devm_gpio_request(&pdev->dev, cs_gpio,
-						dev_name(&pdev->dev));
-				if (ret)
-					goto out;
-			}
-		}
-	}
-
 	init_func = device_get_match_data(&pdev->dev);
 	if (init_func) {
 		ret = init_func(pdev, dwsmmio);