lpc_aspeed: move driver path to class member

Move the driver path to class member.

Change-Id: I83e5c2649ee88ca48f6103dd119fc335e4783338
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/lpc_aspeed.hpp b/lpc_aspeed.hpp
index a6d70af..d6a35af 100644
--- a/lpc_aspeed.hpp
+++ b/lpc_aspeed.hpp
@@ -5,6 +5,7 @@
 
 #include <cstdint>
 #include <memory>
+#include <string>
 #include <utility>
 #include <vector>
 
@@ -28,6 +29,7 @@
     std::vector<std::uint8_t> copyFrom(std::uint32_t length) override;
 
   private:
+    static const std::string lpcControlPath;
     std::size_t regionSize;
     const internal::Sys* sys;
 };