MFC r235981,236394

MFC r235981,236394

 In case forwarding is turned on for a given address family, refuse to
 queue the packet for LRO and tell the driver to directly pass it on.
 This avoids re-assembly and later re-fragmentation problems when
 forwarding.

 It's not the best solution but the simplest and most effective for
 the moment.

 Make TCP LRO work properly with VIMAGE kernels rather than just panicing.
 There's no VIMAGE context set there yet as this is before if_ethersubr.c.

Approved by:	re

git-svn-id: svn://svn.freebsd.org/base/stable/9@238239 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f