PCI: pci_{enable,disable}_device() nestable ports

Change drivers/message/i20 pci driver to simply do a nestable
enable()/disable() instead of checking for it.

Signed-off-by: Inaky Perez-Gonzalez <inaky@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>