ANDROID: GKI: bring back icmpv6_send

In 5.4.102 the icmpv6_send() was replaced with an inline function.
Bring it back to provide for modules that used this symbol to preserve
the ABI.

Bug: 161946584
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: Id1a914518f6e850f6bb96b5449c15eda3a7a7fd8