lpc_aspeed: implement close method

Implement close method on lpc aspeed, such that it'll unmap the memory
region and close the file handle to the driver.

Change-Id: Ie0417fb6c77a2b9d4b4db532b464738b2430a811
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/lpc_aspeed.cpp b/lpc_aspeed.cpp
index 7531382..f1caaa5 100644
--- a/lpc_aspeed.cpp
+++ b/lpc_aspeed.cpp
@@ -45,6 +45,17 @@
 
 void LpcMapperAspeed::close()
 {
+    if (mappedRegion)
+    {
+        sys->munmap(mappedRegion, regionSize);
+        mappedRegion = nullptr;
+    }
+
+    if (mappedFd != -1)
+    {
+        sys->close(mappedFd);
+        mappedFd = -1;
+    }
 }
 
 std::pair<std::uint32_t, std::uint32_t>