net: Fix potential empty DHCP Parameter Request List

Can't get IP address with dhcp due to the dhcp server not
allow the empty param list request under some network env

This patch is based on Gray Remlin's initial patch.

Signed-off-by: Jason Liu <r64343@freescale.com>
Signed-off-by: Gray Remlin <g_remlin@rocketmail.com>
1 file changed