The only caller of this function only cares about gross success/failure
but we still might as well resolve the following smatch warning and fix
the other error paths as well:

    hiddev.c:894 hiddev_connect() warn: returning -1 instead of -ENOMEM is sloppy
Signed-off-by: Jason Gerecke <jason.gerecke@wacom.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>