gprs_bssgp_rim: fix bug in dub_tlvp_header()

When the length field is written the function writes the lower and the
higher half of the length at the same position, so the higher half is
overwritten with the lower half, this is wrong.

Change-Id: I3cce0b2796793554a421fd3ce8e749c52d22eaea
Related: CID#216670
Related: SYS#5103
diff --git a/src/gb/gprs_bssgp_rim.c b/src/gb/gprs_bssgp_rim.c
index 2096977..23fb3a0 100644
--- a/src/gb/gprs_bssgp_rim.c
+++ b/src/gb/gprs_bssgp_rim.c
@@ -438,7 +438,7 @@
 	} else {
 		memmove(buf_ptr + 1, buf_ptr, len);
 		buf_ptr[1] = len >> 8;
-		buf_ptr[1] = len & 0xff;
+		buf_ptr[2] = len & 0xff;
 		buf_ptr += TVLV_HDR_MAXLEN;
 	}
 	buf_ptr += len;