gsm48_ie.c: change bearer cap structure in outgoing CSD calls

Outgoing CSD calls were previously encoded with the
Bearer Capability 1 - Octet 4 "Structure" field set to
3 - Unstructured. Many Nokia, Sony Ericsson and Huawei devices
won't accept incoming CSD calls with these bits set.

Set them to 0 - Service data unit integrity for now, which
seems to work and make all tested devices happy.

Change-Id: Ieb5bca3d3578abd28e18808752e1c312ce7c4ce0
diff --git a/src/gsm/gsm48_ie.c b/src/gsm/gsm48_ie.c
index 7de1f98..bb86cf4 100644
--- a/src/gsm/gsm48_ie.c
+++ b/src/gsm/gsm48_ie.c
@@ -339,7 +339,7 @@
 	case GSM48_BCAP_ITCAP_FAX_G3:
 		lv[i++] |= 0x80; /* last IE of octet 3 etc */
 		/* octet 4 */
-		lv[i++] = 0xb8;
+		lv[i++] = 0x88;
 		/* octet 5 */
 		lv[i++] = 0x80 | ((bcap->data.rate_adaption & 3) << 3)
 			  | (bcap->data.sig_access & 7);
diff --git a/tests/gsm0408/gsm0408_test.c b/tests/gsm0408/gsm0408_test.c
index 5b3f5cd..e82178d 100644
--- a/tests/gsm0408/gsm0408_test.c
+++ b/tests/gsm0408/gsm0408_test.c
@@ -31,7 +31,7 @@
 #include <osmocom/core/msgb.h>
 
 
-static const uint8_t csd_9600_v110_lv[] = { 0x07, 0xa1, 0xb8, 0x89, 0x21, 0x15, 0x63, 0x80 };
+static const uint8_t csd_9600_v110_lv[] = { 0x07, 0xa1, 0x88, 0x89, 0x21, 0x15, 0x63, 0x80 };
 
 static const struct gsm_mncc_bearer_cap bcap_csd_9600_v110 = {
 	.transfer =	GSM48_BCAP_ITCAP_UNR_DIG_INF,