tcm_qla2xxx: Add NPIV specific enable/disable attribute logic

This patch adds seperate logic for NPIV specific enable/disable
attribute logic, as NPIV vs. non-NPIV enable/disable ends up being
different enough to warrent seperate logic for setting configfs
tpg_group dependencies in the non-NPIV case.

Cc: Sawan Chandak <sawan.chandak@qlogic.com>
Cc: Quinn Tran <quinn.tran@qlogic.com>
Cc: Saurav Kashyap <saurav.kashyap@qlogic.com>
Cc: Giridhar Malavali <giridhar.malavali@qlogic.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>