pci_handler: add aspeed-p2a-ctrl path

Add the path to the aspeed-p2a-ctrl device for mapping access.

The need to map, read, etc, is similar to lpc_handler, and they may
converge.

Signed-off-by: Patrick Venture <venture@google.com>
Change-Id: I0b8e7bf1581f77abb819d10dba136569034c21e9
diff --git a/pci_handler.cpp b/pci_handler.cpp
index 3f9b99f..b82d16a 100644
--- a/pci_handler.cpp
+++ b/pci_handler.cpp
@@ -18,11 +18,14 @@
 
 #include <cstdint>
 #include <cstring>
+#include <string>
 #include <vector>
 
 namespace blobs
 {
 
+const std::string PciDataHandler::p2aControlPath = "/dev/aspeed-p2a-ctrl";
+
 bool PciDataHandler::open()
 {
     /* TODO: For the ASPEED P2A driver, this method will enable the memory