tz-ppc: add dummy read/write methods

Add tz-ppc-dummy mmio read/write methods to avoid assert failure
during initialisation.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
Reviewed-by: Li Qiang <liq3ea@gmail.com>
Message-Id: <20200811114133.672647-8-ppandit@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

hw/misc/tz-ppc.c

@@ -196,7 +196,21 @@ static bool tz_ppc_dummy_accepts(void *opaque, hwaddr addr,
     g_assert_not_reached();
 }
 
+static uint64_t tz_ppc_dummy_read(void *opaque, hwaddr addr, unsigned size)
+{
+    g_assert_not_reached();
+}
+
+static void tz_ppc_dummy_write(void *opaque, hwaddr addr,
+                                        uint64_t data, unsigned size)
+{
+    g_assert_not_reached();
+}
+
 static const MemoryRegionOps tz_ppc_dummy_ops = {
+    /* define r/w methods to avoid assert failure in memory_region_init_io */
+    .read = tz_ppc_dummy_read,
+    .write = tz_ppc_dummy_write,
     .valid.accepts = tz_ppc_dummy_accepts,
 };