net: fix some sparse errors

make C=2 CF="-D__CHECK_ENDIAN__" M=net

And fix flowi4_init_output() prototype for sport

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Conflicts:
	include/net/flow.h
	net/ipv4/ping.c