mgmt: hawkbit: fix call to bin2hex

Fixes: f2affbd ("os: lib: bin2hex: fix memory overwrite")
Signed-off-by: Yudong Zhang <mtwget@gmail.com>
diff --git a/subsys/mgmt/hawkbit/hawkbit_device.c b/subsys/mgmt/hawkbit/hawkbit_device.c
index 63434bb..05b9202 100644
--- a/subsys/mgmt/hawkbit/hawkbit_device.c
+++ b/subsys/mgmt/hawkbit/hawkbit_device.c
@@ -17,7 +17,7 @@
 	}
 
 	memset(id, 0, id_max_len);
-	length = bin2hex(hwinfo_id, (size_t)length, id, id_max_len - 1);
+	length = bin2hex(hwinfo_id, (size_t)length, id, id_max_len);
 
 	return length > 0;
 }