hardware interface: add copyFrom

Add a copyFrom method to the hardware window interface and empty
implementations of it within the current lpc handlers.

Change-Id: If2ab6a47763387721edd1a0c451ed8c6087eb475
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/lpc_aspeed.cpp b/lpc_aspeed.cpp
index 62760c5..2001986 100644
--- a/lpc_aspeed.cpp
+++ b/lpc_aspeed.cpp
@@ -96,4 +96,10 @@
     return std::make_pair(offset, length);
 }
 
+std::vector<std::uint8_t> LpcMapperAspeed::copyFrom(std::uint32_t length)
+{
+    /* TODO: Implement this. */
+    return {};
+}
+
 } // namespace blobs