Verify Read Memory Data size on third party devices

[jloehr]

Third party Wii Remotes and Balance Boards may report a wrong size for the valid bytes in a read memory reports (0x21).

BigBen Balance Board seems to always set the size nibble to 0xF, i.e. 16 Bytes, even if non multiple of 16 is requested. For the calibration data that results in writing additional 8 Bytes beyond the array and Balance Board State. Though that needs verification, if that causes any issues.