BootstrapProtocol describes the supported types of bootstrap.
The Primitive SPI protocol is used by OpenTitan during development.
The Legacy SPI protocol is used by previous generations of Google Titan-class chips.
The LegacyRescue UART protocol is used by previous generations of Google Titan-class chips.
The Eeprom SPI protocol is planned to be implemented for OpenTitan.
The ‘Emulator’ value indicates that this tool has a direct way
of communicating with the OpenTitan emulator, to replace the
contents of the emulated flash storage.