[SCSI] qla4xxx: add support for set_net_config

Allows user space (iscsiadm) to send down network configuration
parameters for LLD to set private network configuration on the iSCSI
adapters.

Based on patches from Vikas Chaudhary.

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