bsc_init: fix Werror: define rc for 2quater with si2q_count == 0

  src/libbsc/bsc_init.c: In function ‘rsl_si’:
  src/libbsc/bsc_init.c:153:2: error: ‘rc’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
    return rc;
    ^

Change-Id: Iedad1efcb477c77db8c741777ea076761658c7d1
diff --git a/src/libbsc/bsc_init.c b/src/libbsc/bsc_init.c
index 674813c..fa8c477 100644
--- a/src/libbsc/bsc_init.c
+++ b/src/libbsc/bsc_init.c
@@ -142,6 +142,7 @@
 			rc = rsl_bcch_info(trx, i, NULL, 0);
 			break;
 		}
+		rc = 0;
 		for (j = 0; j <= bts->si2q_count; j++)
 			rc = rsl_bcch_info(trx, i, (const uint8_t *)GSM_BTS_SI2Q(bts, j), GSM_MACBLOCK_LEN);
 		break;