Go back to resetting the refresh counter after a DMA. Probably not quite correct as it is probably reset on VDP triggered refresh, but this is close enough for now given the general limitations with my refresh code. VDP FIFO Testing seems to be passing 100% reliably again (was occassionally failing still with the last commit)

#ifndef PPM_H_
#define PPM_H_

void save_ppm(FILE *f, uint32_t *buffer, uint32_t width, uint32_t height, uint32_t pitch);

#endif //PPM_H_