lpc_aspeed: implement mapRegion as part of copyFrom

For the lpc aspeed ctrl driver, it'll use mmap to map the memory region
instead of using an ioctl.

Change-Id: I884fb5713b4c853cc84c8e994969b385392bdc95
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/lpc_aspeed.hpp b/lpc_aspeed.hpp
index e89662c..56d1479 100644
--- a/lpc_aspeed.hpp
+++ b/lpc_aspeed.hpp
@@ -30,9 +30,17 @@
 
     std::vector<std::uint8_t> copyFrom(std::uint32_t length) override;
 
+    /**
+     * Attempt to mmap the region.
+     *
+     * @return true on success, false otherwise.
+     */
+    bool mapRegion();
+
   private:
     static const std::string lpcControlPath;
     int mappedFd = -1;
+    std::uint8_t* mappedRegion = nullptr;
     std::uint32_t regionAddress;
     std::size_t regionSize;
     const internal::Sys* sys;