tests/hnb-test: Fix signedness of assigned pointer

Change-Id: I320ad86b83b0308b43489e8d95f63d6ed55821b5
diff --git a/src/tests/hnb-test.c b/src/tests/hnb-test.c
index 4650a90..7824858 100644
--- a/src/tests/hnb-test.c
+++ b/src/tests/hnb-test.c
@@ -667,7 +667,7 @@
 	asn1_u8_to_str(&request.rac, &rac, rac);
 	asn1_u28_to_bitstring(&request.cellIdentity, &cid, cid);
 
-	request.hnB_Identity.hNB_Identity_Info.buf = identity;
+	request.hnB_Identity.hNB_Identity_Info.buf = (uint8_t*) identity;
 	request.hnB_Identity.hNB_Identity_Info.size = strlen(identity);
 
 	request.plmNidentity.buf = plmn;