firmware: move enum into class

This will protect the namespace from pollution, but also allow it to be
just a normal enum for arithmetic operations.

Change-Id: Ie4eab4040619b0c37ab0395b984437ebf3cf2101
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/firmware_handler.hpp b/firmware_handler.hpp
index 1a9e8b0..8f54d7d 100644
--- a/firmware_handler.hpp
+++ b/firmware_handler.hpp
@@ -11,19 +11,19 @@
 namespace blobs
 {
 
-enum class FirmwareUpdateFlags
-{
-    bt = (1 << 8),   /* Expect to send contents over IPMI BlockTransfer. */
-    p2a = (1 << 9),  /* Expect to send contents over P2A bridge. */
-    lpc = (1 << 10), /* Expect to send contents over LPC bridge. */
-};
-
 /**
  * Register only one firmware blob handler that will manage all sessions.
  */
 class FirmwareBlobHandler : public GenericBlobInterface
 {
   public:
+    enum FirmwareUpdateFlags : std::uint16_t
+    {
+        bt = (1 << 8),   /* Expect to send contents over IPMI BlockTransfer. */
+        p2a = (1 << 9),  /* Expect to send contents over P2A bridge. */
+        lpc = (1 << 10), /* Expect to send contents over LPC bridge. */
+    };
+
     /**
      * Create a FirmwareBlobHandler.
      *