Fix hex vs decimal bug in error message from MP7 "check firmware version" command

Since the stream operator (i.e. operator<<) for xdata::Serializable is defined locally within SWATCH, and based on the toString method, it cannot take into account the std::ios format flags, such as std::ios_base.

As a result, when testing some calo layer 2 firmware that was based on infra v2.2.1, with key that expected infra version 2.4.0, the MP7 'check firmware version' command created the following message

Infra Firmware mismatch - Expected: 0x132096 Found: 0x20201

The first number here, 132096 is equal to 0x20400 formatted with decimal base. The MP7 'check firmware version' command should be updated to display the expected firmware version number with a hex base.