firmwarehandler: Provide a factory for building

Provide a factory for building the firmware blob handler.  This allows
us to later provide built-time parameters to the handler through the
constructor and not within the object itself.

Change-Id: I19c90de45eaf65b78dfd55beb61f2ad4cc6fa43e
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/firmware_handler.hpp b/firmware_handler.hpp
index ada0c14..e22c335 100644
--- a/firmware_handler.hpp
+++ b/firmware_handler.hpp
@@ -1,6 +1,7 @@
 #pragma once
 
 #include <blobs-ipmid/blobs.hpp>
+#include <memory>
 
 namespace blobs
 {
@@ -18,6 +19,8 @@
 class FirmwareBlobHandler : public GenericBlobInterface
 {
   public:
+    static std::unique_ptr<GenericBlobInterface> CreateFirmwareBlobHandler();
+
     FirmwareBlobHandler() = default;
     ~FirmwareBlobHandler() = default;
     FirmwareBlobHandler(const FirmwareBlobHandler&) = default;