Add a helper to directly set the SO_LINGER sockopt from kernel space
with onoff set to true and a linger time of 0 without going through a
fake uaccess.
Signed-off-by: Christoph Hellwig <hch@lst.de> Acked-by: Sagi Grimberg <sagi@grimberg.me> Signed-off-by: David S. Miller <davem@davemloft.net>