spi: fsl: use platform_get_irq() instead of of_irq_to_resource()

Unlike irq_of_parse_and_map() which has a dummy definition on SPARC,
of_irq_to_resource() hasn't.

But as platform_get_irq() can be used instead and is generic, use it.
Reported-by: kbuild test robot <lkp@intel.com>
Suggested-by: Mark Brown <broonie@kernel.org>
Fixes: 	3194d253 ("spi: fsl: don't map irq during probe")
Cc: stable@vger.kernel.org
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Link: https://lore.kernel.org/r/091a277fd0b3356dca1e29858c1c96983fc9cb25.1576172743.git.christophe.leroy@c-s.frSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-fsl-spi.c

@@ -746,9 +746,9 @@ static int of_fsl_spi_probe(struct platform_device *ofdev)
 	if (ret)
 		goto err;
 
-	irq = of_irq_to_resource(np, 0, NULL);
-	if (irq <= 0) {
-		ret = -EINVAL;
+	irq = platform_get_irq(ofdev, 0);
+	if (irq < 0) {
+		ret = irq;
 		goto err;
 	}