Fix abs() warning in dd_controller.c

[Rosalie241]

This fixes the following compiler warning:

    CC  _obj/device/dd/dd_controller.o
../../src/device/dd/dd_controller.c: In function ‘write_dd_regs’:
../../src/device/dd/dd_controller.c:512:30: warning: taking the absolute value of unsigned type ‘unsigned int’ has no effect [-Wabsolute-value]
  512 |             cycles += 4825 * abs(track - old_track);
      |                              ^~~
../../src/device/dd/dd_controller.c:547:30: warning: taking the absolute value of unsigned type ‘unsigned int’ has no effect [-Wabsolute-value]
  547 |             cycles += 4825 * abs(track - old_track);
      |               

I've asked @LuigiBlood for advice on what to change and this is the result of that.