misc: silence -Wmaybe-uninitialized warnings

GCC 12 complains about such errors while the code itself looks good.

Type: fix
Signed-off-by: Jieqiang Wang <jieqiang.wang@arm.com>
Change-Id: I021719fdbf7d9bd93a12eac76aeac8cbca13a810
diff --git a/src/vnet/tcp/tcp_output.c b/src/vnet/tcp/tcp_output.c
index c8e80d0..aad69df 100644
--- a/src/vnet/tcp/tcp_output.c
+++ b/src/vnet/tcp/tcp_output.c
@@ -420,7 +420,7 @@
 tcp_make_ack_i (tcp_connection_t * tc, vlib_buffer_t * b, tcp_state_t state,
 		u8 flags)
 {
-  tcp_options_t _snd_opts, *snd_opts = &_snd_opts;
+  tcp_options_t _snd_opts = {}, *snd_opts = &_snd_opts;
   u8 tcp_opts_len, tcp_hdr_opts_len;
   tcp_header_t *th;
   u16 wnd;