When building in release mode on OVMF, the ASSERT_EFI_ERROR
macro is empty. So, to set the BootMode, in a release build,
it must be outside of ASSERT_EFI_ERROR.
git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@11413 6f19259b-4bc3-4df7-8a09-765794883524