flashid (almost) always contains the hexadecimal representation of two
bytes, which then means it gets compares with strcmp, which in turn need
another string argument. Instead, make it an integer, removing the need to
call strcmp.
Add a separate string representation for printing purposes (maybe this can be
avoided by having the print function format it when needed ?).
The only apparent case where flashid is not an hexadecimal representation
of a pair of bytes is when N64 clears it to "CONF". Set flashid to zero
this case.
This saves about 500 bytes of program space and 200 bytes of ram.
