added prach buffer for if4p5 processing in RRU. This fixed a critical bug which was seen for bandwidths greater than 5 MHz. RRU tested with 5/10 MHz on 1.5 GHz Atom.

targets/ARCH/COMMON/common_lib.h

@@ -249,6 +249,8 @@ typedef struct {
 typedef struct {
   //! Tx buffer for if device
   void *tx;
+  //! Tx buffer (PRACH) for if device
+  void *tx_prach;
   //! Rx buffer for if device
   void *rx;
 } if_buffer_t;