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>