net: ipv6: Generate random IID for addresses on RAWIP devices

RAWIP devices such as rmnet do not have a hardware address and
instead require the kernel to generate a random IID for the
IPv6 addresses.

CRs-Fixed: 2233026
Change-Id: Ic46b85f43e4e87cc463d214f8085ffc5584e31f0
Signed-off-by: Sean Tranchetti <stranche@codeaurora.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Git-commit: 9deb441c113ae9e761e42f78d90736d762ff49a3
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>