[SCSI] qla4xxx: fix data alignment and use nl helpers

This has the driver use helpers for a common operation and fixes
a issue where if multiple iscsi params are sent they could be
sent at offsets that cause unaligned accesses. The nla helpers
account for the padding needed to align properly for the driver.

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>