spi: s3c64xx: Allow controller-data to be optional

The Samsung SoC SPI driver requires to provide controller-data node
for each of SPI peripheral device nodes.  Make this controller-data node
optional, so DTS could be simpler.
Suggested-by: Rob Herring <robh@kernel.org>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Reviewed-by: Sam Protsenko <semen.protsenko@linaro.org>
Reviewed-by: Andi Shyti <andi@etezian.org>
Reviwed-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20220124082347.32747-5-krzysztof.kozlowski@canonical.com

drivers/spi/spi-s3c64xx.c

@@ -796,16 +796,14 @@ static struct s3c64xx_spi_csinfo *s3c64xx_get_slave_ctrldata(
 		return ERR_PTR(-EINVAL);
 	}
 
-	data_np = of_get_child_by_name(slave_np, "controller-data");
-	if (!data_np) {
-		dev_err(&spi->dev, "child node 'controller-data' not found\n");
-		return ERR_PTR(-EINVAL);
-	}
-
 	cs = kzalloc(sizeof(*cs), GFP_KERNEL);
-	if (!cs) {
-		of_node_put(data_np);
+	if (!cs)
 		return ERR_PTR(-ENOMEM);
+
+	data_np = of_get_child_by_name(slave_np, "controller-data");
+	if (!data_np) {
+		dev_info(&spi->dev, "feedback delay set to default (0)\n");
+		return cs;
 	}
 
 	of_property_read_u32(data_np, "samsung,spi-feedback-delay", &fb_delay);