net: ipv4: increase dhcp inter device timeout

net: ipv4: increase dhcp inter device timeout

When a system has multiple ethernet devices and during DHCP
request (for using NFS), the system waits only for HZ/2 which is
500mS before switching to another interface for DHCP.

There are some routers (Ex: Trendnet routers) which responds to
DHCP request at about 560mS. When the system has only one
ethernet interface there is no issue as the timeout is 2S and the
dev xid doesn't changes and only retries.

But when the system has multiple Ethernet like DRA74x with CPSW
in dual EMAC mode, the DHCP response is dropped as the dev xid
changes while shifting to the next device. So changing inter
device timeout to HZ (which is 1S).

Signed-off-by: Mugunthan V N <mugunthanvnm@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>