trafgen: xilinx: Added support for Static and Streaming Modes.

This patch adds support for Static Mode and Streaming Mode.
Use case: Streaming mode is used to stress the different Streaming
interfaces. Static mode is used to generate the required burst length
transactions.

Signed-off-by: Kedareswara rao Appana <appanad@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>