ipv6: Inhibit IPv4-mapped src address on the wire.

[ Upstream commit ec5e3b0a1d41fbda0cc33a45bc9e54e91d9d12c7 ]

This patch adds a check for the problematic case of an IPv4-mapped IPv6
source address and a destination address that is neither an IPv4-mapped
IPv6 address nor in6addr_any, and returns an appropriate error. The
check in done before returning from looking up the route.

Signed-off-by: Jonathan T. Leighton <jtleight@udel.edu>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>