Fix inconsistent type of global ue_id_g

Found by -fsanitize=address

```
=================================================================
==35428==ERROR: AddressSanitizer: global-buffer-overflow on
address 0x0000021039a0 at pc 0x000000566dd6 bp 0x7ffc7974ccd0 sp
0x7ffc7974ccc0
WRITE of size 4 at 0x0000021039a0 thread T0
    #0 0x566dd5 in main
    targets/RT/USER/lte-uesoftmodem.c:629
    #1 0x7f36223cb83f in __libc_start_main
    (/lib/x86_64-linux-gnu/libc.so.6+0x2083f)
    #2 0x582218 in _start
    (cmake_targets/ran_build/build/lte-uesoftmodem+0x582218)
```

openair2/LAYER2/PDCP_v10.1.0/pdcp.h

@@ -545,5 +545,7 @@ extern notifiedFIFO_t         pdcp_sdu_list;
 
 extern hash_table_t  *pdcp_coll_p;
 
+extern uint16_t ue_id_g;
+
 #endif
 /*@}*/

openair2/PHY_INTERFACE/phy_stub_UE.c

@@ -1187,7 +1187,7 @@ void ue_init_standalone_socket(int tx_port, int rx_port)
 
     if (inet_pton(server_address.sin_family, stub_eth_params.remote_addr, &server_address.sin_addr) <= 0)
     {
-      LOG_E(MAC, "Invalid standalone PNF Address\n");
+      LOG_E(MAC, "Invalid standalone PNF Address '%s'\n", stub_eth_params.remote_addr);
       close(sd);
       return;
     }

targets/RT/USER/lte-uesoftmodem.c

@@ -86,8 +86,6 @@
 
 #include "lte-softmodem.h"
 
-extern int ue_id_g;
-
 /* temporary compilation wokaround (UE/eNB split */