net: Use more bit fields in napi_gro_cb

[ Upstream commit baa32ff42871f2d4aca9c08c9403d0e497325564 ]

This patch moves the free and same_flow fields to be bit fields
(2 and 1 bit sized respectively). This frees up some space for u16's.

Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>