pcmcia: make use of pcmcia_dev_resume() return value

In runtime_resume(), do not throw away the return value of
pcmcia_dev_resume(), for we can use it (at least) in
pcmcia_store_pm_state(). This also fixes the pointless assignment
previosly seen there, as noted by Dan Carpenter.

CC: Dan Carpenter <error27@gmail.com>
Tested-by: Wolfram Sang <w.sang@pengutronix.de>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>