Make gcc 11.1.0 false positivies happy

After my system's gcc was upgraded, I get false positivies like the one
below:
"""
/git/osmo-pcu/src/gprs_bssgp_pcu.c: In function ‘ns_configure_nse’:
/git/osmo-pcu/src/gprs_bssgp_pcu.c:1103:58: error: ‘%d’ directive output may be truncated writing between 1 and 11 bytes into a region of size 2 [-Werror=format-truncation=]
 1103 |                         snprintf(name, sizeof(name), "pcu%d", i);
      |                                                          ^~
/git/osmo-pcu/src/gprs_bssgp_pcu.c:1103:54: note: directive argument in the range [-2147483648, 1]
 1103 |                         snprintf(name, sizeof(name), "pcu%d", i);
      |                                                      ^~~~~~~
/git/osmo-pcu/src/gprs_bssgp_pcu.c:1103:25: note: ‘snprintf’ output between 5 and 15 bytes into a destination of size 5
 1103 |                         snprintf(name, sizeof(name), "pcu%d", i);
      |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
"""
In this case, i can't never take a value with more than 1 digit, but gcc
seems to be unable to see that.

Let's increase the buffer size a few bytes to make gcc happy, and make
the variable unsigned since it never will get negative values.

Next change is also a false positive, since variables are always
initialized beforehand in the cod epaths where they are used:
"""
/git/osmo-pcu/src/bts.cpp: In function ‘int bts_rcv_rach(gprs_rlcmac_bts*, const rach_ind_params*)’:
/git/osmo-pcu/src/bts.cpp:859:25: error: ‘ts_no’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
  859 |         uint8_t trx_no, ts_no;
      |                         ^~~~~
/git/osmo-pcu/src/bts.cpp:859:17: error: ‘trx_no’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
  859 |         uint8_t trx_no, ts_no;
      |                 ^~~~~~
"""

Change-Id: I1362a335a0c761bde367dbc779de4afa88f13584
diff --git a/src/gprs_bssgp_pcu.c b/src/gprs_bssgp_pcu.c
index 0e8e145..e2f6f51 100644
--- a/src/gprs_bssgp_pcu.c
+++ b/src/gprs_bssgp_pcu.c
@@ -1075,12 +1075,13 @@
 			    const uint16_t *nsvci,
 			    uint16_t valid)
 {
-	int i, rc;
+	unsigned int i;
+	int rc;
 	uint16_t binds = 0;
 	bool nsvcs = false;
 	struct gprs_ns2_vc *nsvc;
 	struct gprs_ns2_vc_bind *bind[PCU_IF_NUM_NSVC] = { };
-	char name[5];
+	char name[16];
 	bool sns_configured = false;
 
 	if (!valid)
@@ -1100,7 +1101,7 @@
 			continue;
 
 		if (!gprs_ns2_ip_bind_by_sockaddr(the_pcu->nsi, &local[i])) {
-			snprintf(name, sizeof(name), "pcu%d", i);
+			snprintf(name, sizeof(name), "pcu%u", i);
 			rc = gprs_ns2_ip_bind(the_pcu->nsi, name, &local[i], 0, &bind[i]);
 			if (rc < 0) {
 				LOGP(DBSSGP, LOGL_ERROR, "Failed to bind to %s\n", osmo_sockaddr_to_str(&local[i]));