socket: add support for Linux timestamping transmit IDs

Add a new field to the SCK_Message structure to enable setting and
getting of the Linux timestamping transmit IDs enabled by the
SOF_TIMESTAMPING_OPT_ID socket option. The ID can be set for each packet
individually by the SCM_TS_OPT_ID control message (supported on Linux
6.13 and newer).

This will allow procesing of transmit timestamps without extracting data
from the data-link frames.

socket.h

@@ -67,6 +67,7 @@ typedef struct {
     int if_index;
     int l2_length;
     int tx_flags;
+    uint32_t tx_id;
   } timestamp;
 
   int descriptor;