At the moment only ifup stuff turns netif up.
After the commit f0624a701513 ('net: Do not route traffic
to interfaces that are not up') the dhcp command
keeps netif->ifup == false and network subsystem
can't route packets.

How to repropduce the problem on qemu-malta_defconfig:

    qemu-system-mips -nodefaults -M malta -m 256 \
                     -nographic -serial stdio -monitor null \
                     -bios barebox-flash-image \
                     -net user -net nic,model=rtl8139

    ...

    barebox:/ dhcp
    eth0: 100Mbps full duplex link detected
    eth0: DHCP client bound to address 10.0.2.15
    barebox:/ ping 10.0.2.2
    ping failed: No route to host

However if ifup command is used for network interface
configuration then there is no network problem, e.g.

    barebox:/ ifup eth0
    eth0: 100Mbps full duplex link detected
    eth0: DHCP client bound to address 10.0.2.15
    barebox:/ ping 10.0.2.2
    host 10.0.2.2 is alive

Signed-off-by: Antony Pavlov <antonynpavlov@gmail.com>
CC: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>