In FDD mode the tx_valid_* signals are generated inside the axi_ad9361_tx module, in function of
the selected dac data rate. In TDD mode, these signals are gated by the tdd_enable and tdd_tx_dp_en signals.
In other words, the tx_valid_* signals will be valid just when tdd_enable and tdd_tx_dp_en is active.
+ Delete unnecessary registers
+ Add the module ad_addsub.v to resolve additions and subtractions inside TDD control
+ Redefine the burst logic
+ Redesign the control signal generations
+ Note: This patch fix the TDD related timing violations