i2c: pca-platform: Use platform_irq_get_optional

The interrupt is not required so use platform_irq_get_optional() to
avoid error messages like

  i2c-pca-platform 22080000.i2c: IRQ index 0 not found
Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

drivers/i2c/busses/i2c-pca-platform.c

@@ -140,7 +140,7 @@ static int i2c_pca_pf_probe(struct platform_device *pdev)
 	int ret = 0;
 	int irq;
 
-	irq = platform_get_irq(pdev, 0);
+	irq = platform_get_irq_optional(pdev, 0);
 	/* If irq is 0, we do polling. */
 	if (irq < 0)
 		irq = 0;