NetworkPkg/NetworkPkg.dec: Update comments for the PCD

NetworkPkg/NetworkPkg.dec: Update comments for the PCD

Update comment section for the PCD PcdIScsiAIPNetworkBootPolicy.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Hegde Nagaraj P <nagaraj-p.hegde@hpe.com>
Reviewed-by: Wu Jiaxin <jiaxin.wu@intel.com>
Reviewed-by: Sriram Subramanian <sriram-s@hpe.com>
Reviewed-by: Zhang Lubo <lubo.zhang@intel.com>
Reviewed-by: Ye Ting <ting.ye@intel.com>
Reviewed-by: Fu Siyuan <siyuan.fu@intel.com>