phosphor-ipmi-flash: Fix all C++ warnings

Change-Id: I89236b2dab88ca725e269bb8f5b2cbfd271e807a
Signed-off-by: Willy Tu <wltu@google.com>
diff --git a/bmc/firmware-handler/test/firmware_multiplebundle_unittest.cpp b/bmc/firmware-handler/test/firmware_multiplebundle_unittest.cpp
index 58f07c7..0a032e8 100644
--- a/bmc/firmware-handler/test/firmware_multiplebundle_unittest.cpp
+++ b/bmc/firmware-handler/test/firmware_multiplebundle_unittest.cpp
@@ -109,8 +109,8 @@
     TriggerMock *biosPrepareMockPtr, *biosVerifyMockPtr, *biosUpdateMockPtr;
 
     std::uint16_t session = 1;
-    std::uint16_t flags =
-        blobs::OpenFlags::write | FirmwareFlags::UpdateFlags::ipmi;
+    std::uint16_t flags = static_cast<std::uint16_t>(blobs::OpenFlags::write) |
+                          FirmwareFlags::UpdateFlags::ipmi;
 };
 
 TEST_F(IpmiOnlyTwoFirmwaresTest, OpeningBiosAfterBlobFails)