fatfs: Fix sec count by FAT
fatfs: Fix sec count by FAT

It's really ok to be 1 or 2. Previously it was smth like
sector_count / byte_per_sec. Of course, it's mistake.

embox/embox,Kakadu/embox,embox/embox,mike2390/embox,Kakadu/embox,gzoom13/embox,mike2390/embox,gzoom13/embox,Kakadu/embox,embox/embox,gzoom13/embox,Kakadu/embox,gzoom13/embox,Kakadu/embox,mike2390/embox,embox/embox,gzoom13/embox,gzoom13/embox,embox/embox,mike2390/embox,embox/embox,mike2390/embox,gzoom13/embox,mike2390/embox,Kakadu/embox,Kakadu/embox,mike2390/embox