Refactor NR_UE_L2_STATE_t enum definition using X-Macro

- this change simplifies the enum definition and makes it easier
  to add, remove, or modify states in the future
- the states are now defined in the NR_UE_L2_STATES macro,
  and the enum members are generated automatically from this macro

openair2/LAYER2/NR_MAC_UE/mac_defs.h

@@ -163,12 +163,18 @@
 #define PRACH_MASK_INDEX                54
 #define RESERVED_NR_DCI                 55
 
+// Define the UE L2 states with X-Macro
+#define NR_UE_L2_STATES \
+  UE_STATE(UE_NOT_SYNC) \
+  UE_STATE(UE_SYNC) \
+  UE_STATE(UE_PERFORMING_RA) \
+  UE_STATE(UE_CONNECTED)
+
 /*!\brief UE layer 2 status */
 typedef enum {
-  UE_NOT_SYNC = 0,
-  UE_SYNC,
-  UE_PERFORMING_RA,
-  UE_CONNECTED
+#define UE_STATE(state) state,
+  NR_UE_L2_STATES
+#undef UE_STATE
 } NR_UE_L2_STATE_t;
 
 typedef enum {