misc: Use g_assert_not_reached for code which is expected to be unreachable

The macro g_assert_not_reached is a better self documenting replacement
for assert(0) or assert(false).

Signed-off-by: Stefan Weil <sw@weilnetz.de>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
diff --git a/net/eth.c b/net/eth.c
index 1d7494d..7c61132 100644
--- a/net/eth.c
+++ b/net/eth.c
@@ -73,7 +73,7 @@
     }
 
     /* Unsupported offload */
-    assert(false);
+    g_assert_not_reached();
 
     return VIRTIO_NET_HDR_GSO_NONE | ecn_state;
 }