nes: remove unused 'timeval' struct member

There is a stale entry in nes_cm_tcp_context that has apparently
never been used in mainline linux.

I'm trying to kill off all users of timeval as part of the
y2038-safety work, so let's just remove this one.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>