edu: mmio: allow 64-bit access

The edu spec says the MMIO area can be accessed by 64-bit.
However currently the 'max_access_size' is not so the MMIO
access dispatch can only access 32-bit one time. This patch fixes
this to respect the spec.
Signed-off-by: NLi Qiang <liq3ea@163.com>
Reviewed-by: NPhilippe Mathieu-Daude <philmd@redhat.com>
Message-Id: <20190510164349.81507-2-liq3ea@163.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

hw/misc/edu.c

@@ -289,6 +289,15 @@ static const MemoryRegionOps edu_mmio_ops = {
     .read = edu_mmio_read,
     .write = edu_mmio_write,
     .endianness = DEVICE_NATIVE_ENDIAN,
+    .valid = {
+        .min_access_size = 4,
+        .max_access_size = 8,
+    },
+    .impl = {
+        .min_access_size = 4,
+        .max_access_size = 8,
+    },
+
 };
 
 /*