spi/ppc4xx: Combine substrings for a message in spi_ppc4xx_of_probe()

The script "checkpatch.pl" pointed information out like the following.

WARNING: quoted string split across lines

Thus fix the affected source code place.
Signed-off-by: NMarkus Elfring <elfring@users.sourceforge.net>
Signed-off-by: NMark Brown <broonie@kernel.org>

drivers/spi/spi-ppc4xx.c

@@ -428,8 +428,9 @@ static int spi_ppc4xx_of_probe(struct platform_device *op)
 				/* Real CS - set the initial state. */
 				ret = gpio_request(gpio, np->name);
 				if (ret < 0) {
-					dev_err(dev, "can't request gpio "
-							"#%d: %d\n", i, ret);
+					dev_err(dev,
+						"can't request gpio #%d: %d\n",
+						i, ret);
 					goto free_gpios;
 				}