Expand mirror functionality

Expand mirror functionality

In order to deal with non-symmetrical load, the mirror function can now
change the packet size of each packet it receives. It can also send the
incoming packet multiple times on each of the tx ports. To support this
feature, 2 new parameters in the cfg file have been added for the mirror
mode:
- multiplier: specifies how many times a packet needs to be sent on each
  tx port. Default is 1.
- mirror_size: the size of the packets that need to be sent. This will
  just change (increase) the packet size of each incoming packet. If not
  specified or invalid value (e.g. <64), the size will not be changed.
The packet size will only be changed for IPv4 UDP and IPv4 TCP.
Note that these parameters have no effect on the mirror copy submode.

Change-Id: Ic46b52abdd80ed51cffee667bd04ade9ec23ff6d
Signed-off-by: Luc Provoost <luc.provoost@intel.com>