pcmcia: avoid sysfs-related lockup for cardbus

In cb_free(), we remove some sysfs files -- other sysfs files might
grab ops_mutex, so we cannot hold it while removing sysfs files. This
fixes http://lkml.org/lkml/2010/1/17/88

 .

Tested-by: Wolfram Sang <w.sang@pengutronix.de>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>