HSI: nokia-modem: Add a space character for better code readability in nokia_modem_probe()

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

ERROR: space required before the open parenthesis '('

Thus fix the affected source code place.
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>

drivers/hsi/clients/nokia-modem.c

@@ -179,7 +179,7 @@ static int nokia_modem_probe(struct device *dev)
 	}
 	enable_irq_wake(irq);
 
-	if(pm) {
+	if (pm) {
 		err = nokia_modem_gpio_probe(dev);
 		if (err < 0) {
 			dev_err(dev, "Could not probe GPIOs\n");