[WCNCR00164904] misc: Fix compile fail with CONFIG_IPV6 disabled

[Description]
Fix compile fail with CONFIG_IPV6 disabled

Wrapping codes with CONFIG_IPV6 macros properly

Change-Id: I5f0c189baecb239bc943a3e9e3c6da582c160fc1
Signed-off-by: Deren Wu <deren.wu@mediatek.com>
CR-Id: WCNCR00164904
Feature: misc
(cherry picked from commit 46d5cf0ca09da7b84c6e7525017da12168bd01a8)
2 files changed