ANDROID: GKI: fix up CRC change with struct skbuff

Commit f1d5e6a5 ("tcp: drop secpath at the same time as we currently
drop dst") added a new include file to tcp.h which messes with the CRC
generation logic.  Fix that up by gating that with __GENKSYMS__

Fixes: f1d5e6a5 ("tcp: drop secpath at the same time as we currently drop dst")
Change-Id: Ib6935ace350bdba0ac3060a776fc38a0e3aab47e
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>