fix compile warning in db.c
diff --git a/openbsc/src/db.c b/openbsc/src/db.c
index 369505a..5dfefb5 100644
--- a/openbsc/src/db.c
+++ b/openbsc/src/db.c
@@ -265,7 +265,7 @@
 {
 	dbi_result result;
 	const char *string;
-	unsigned int cm1;
+	unsigned char cm1;
 	const unsigned char *cm2, *cm3;
 	struct gsm_equipment *equip = &subscr->equipment;