tcp: Honor the eor bit in tcp_mtu_probe

[ Upstream commit 808cf9e38cd7923036a99f459ccc8cf2955e47af ]

Avoid SKB coalescing if eor bit is set in one of the relevant
SKBs.

Fixes: c134ecb8 ("tcp: Make use of MSG_EOR in tcp_sendmsg")
Signed-off-by: Ilya Lesokhin <ilyal@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>