firmware: add write method

The write() method is how the different firmware handlers will receive
data from the update process.

Change-Id: I550a25f69272bae917309956fef798bc3d4eed2e
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/static_handler.hpp b/static_handler.hpp
index d1cca08..65076d7 100644
--- a/static_handler.hpp
+++ b/static_handler.hpp
@@ -2,8 +2,10 @@
 
 #include "image_handler.hpp"
 
+#include <cstdint>
 #include <memory>
 #include <string>
+#include <vector>
 
 namespace blobs
 {
@@ -18,6 +20,9 @@
 
     bool open(const std::string& path) override;
 
+    bool write(std::uint32_t offset,
+               const std::vector<std::uint8_t>& data) override;
+
   private:
     std::string path;
 };