[BRIDGE]: Remove unused include of a header file in ebtables.c

In net/bridge/netfilter/ebtables.c,
- remove unused include of a header file (linux/tty.h) and remove the
  corresponding comment above it.

Signed-off-by: Rami Rosen <ramirose@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>