pata_ixp4xx_cf: fix oops on detach

pata_ixp4xx_cf dodged dont-clear-drvdata-in-LLD bombing run as it used
platform_set_drvdata() instead of dev_set_drvdata().  This causes OOPS
on devres host release.  Kill it.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>