spi: pxa2xx: Provide num-cs for Sharp PDAs via device properties

Since driver can parse num-cs device property, replace platform data
with this new approach. This pursues the following objectives:

- getting rid of the public header that barely used outside of
  the SPI subsystem (more specifically the SPI PXA2xx drivers)

- making a trampoline for the driver to support non-default number
  of the chip select pins in case the original code is going to be
  converted to Device Tree model

It's not expected to have more users in board files except this one.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20240417110334.2671228-3-andriy.shevchenko@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

arch/arm/mach-pxa/spitz.c

@@ -18,10 +18,10 @@
 #include <linux/i2c.h>
 #include <linux/platform_data/i2c-pxa.h>
 #include <linux/platform_data/pca953x.h>
+#include <linux/property.h>
 #include <linux/spi/spi.h>
 #include <linux/spi/ads7846.h>
 #include <linux/spi/corgi_lcd.h>
-#include <linux/spi/pxa2xx_spi.h>
 #include <linux/mtd/sharpsl.h>
 #include <linux/mtd/physmap.h>
 #include <linux/input-event-codes.h>
@@ -569,10 +569,6 @@ static struct spi_board_info spitz_spi_devices[] = {
 	},
 };
 
-static struct pxa2xx_spi_controller spitz_spi_info = {
-	.num_chipselect	= 3,
-};
-
 static struct gpiod_lookup_table spitz_spi_gpio_table = {
 	.dev_id = "spi2",
 	.table = {
@@ -583,10 +579,20 @@ static struct gpiod_lookup_table spitz_spi_gpio_table = {
 	},
 };
 
+static const struct property_entry spitz_spi_properties[] = {
+	PROPERTY_ENTRY_U32("num-cs", 3),
+	{ }
+};
+
+static const struct software_node spitz_spi_node = {
+	.properties = spitz_spi_properties,
+};
+
 static void __init spitz_spi_init(void)
 {
 	struct platform_device *pd;
 	int id = 2;
+	int err;
 
 	if (machine_is_akita())
 		gpiod_add_lookup_table(&akita_lcdcon_gpio_table);
@@ -601,9 +607,14 @@ static void __init spitz_spi_init(void)
 	if (pd == NULL) {
 		pr_err("pxa2xx-spi: failed to allocate device id %d\n", id);
 	} else {
-		pd->dev.platform_data = &spitz_spi_info;
+		err = device_add_software_node(&pd->dev, &spitz_spi_node);
+		if (err) {
+			platform_device_put(pd);
+			pr_err("pxa2xx-spi: failed to add software node\n");
+		} else {
 			platform_device_add(pd);
 		}
+	}
 
 	spi_register_board_info(ARRAY_AND_SIZE(spitz_spi_devices));
 }