sql: fix 3g_auc's column K data type

K is the SIM card's 128bit secret key, so the type should be VARCHAR like the
other key columns. The db code already reads the column as text and parses as
hex, so a VARCHAR column matches that.

Change-Id: Iaa8d33e303760bd15dcb7dc8bb8b9b24bf6c8f14

sql/hlr.sql

@@ -60,7 +60,7 @@ CREATE TABLE auc_2g (
 CREATE TABLE auc_3g (
 	subscriber_id	INTEGER PRIMARY KEY,	-- subscriber.id
 	algo_id_3g	INTEGER NOT NULL,
-	k		INTEGER NOT NULL,
+	k		VARCHAR(32) NOT NULL,
 	op		VARCHAR,
 	opc		VARCHAR,
 	sqn		INTEGER