pcmcia: fix unused function compile warning

pcmcia_socket_dev_resume() is only referenced from macro
SET_SYSTEM_SLEEP_PM_OPS(NULL, pcmcia_socket_dev_resume)
which based on CONFIG_PM_SLEEP may or may not actually
use its second parameter.
Signed-off-by: Maciej Żenczykowski <zenczykowski@gmail.com>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>

drivers/pcmcia/cs.c

@@ -844,7 +844,7 @@ static int pcmcia_socket_dev_resume_noirq(struct device *dev)
 	return __pcmcia_pm_op(dev, socket_early_resume);
 }
 
-static int pcmcia_socket_dev_resume(struct device *dev)
+static int __used pcmcia_socket_dev_resume(struct device *dev)
 {
 	return __pcmcia_pm_op(dev, socket_late_resume);
 }