x2gokdriveremote.c: fix OsTimerCallback FTBFS on 32-bit platforms.

OSTimerCallback has been returning CARD32 for the past 12 years, but our code used callbacks with unsigned int. Since unsigned int's size changes with hardware architecture on some systems (including Linux), it was only a matter of time until this breaks.

Luckily, we can just change your code to also always return CARD32 and be done with it.