ipv4: use RT_TOS after some rt_tos conversions

[ Upstream commit b0fe4a31 ]

rt_tos was changed to iph->tos but it must be filtered by RT_TOS

Signed-off-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>