iwlagn: sysfs couldn't find the priv pointer

This bug has been introduced by:
d5934110
Author: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Date:   Mon Jul 11 10:48:51 2011 +0300

    iwlagn: simplify the bus architecture

Revert part of the buggy patch: dev_get_drvdata will now return
iwl_priv as it did before the patch.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>