Make ErrorDevice UNCACHEABLE instead of UNCACHED

...even though it still supports Acquire.  This avoids needing to flush
the D$ on FENCE.I because of the presence of the ErrorDevice.

src/main/scala/devices/tilelink/Error.scala

@@ -26,7 +26,7 @@ abstract class DevNullDevice(params: ErrorParams, beatBytes: Int = 4)
     Seq(TLManagerParameters(
       address            = params.address,
       resources          = device.reg("mem"),
-      regionType         = RegionType.UNCACHED,
+      regionType         = RegionType.UNCACHEABLE,
       executable         = true,
       supportsAcquireT   = xfer,
       supportsAcquireB   = xfer,