ff.c : fix fallthrough warning

[gullradriel]

That PR fix the following warning introduced when enabling EXFAT :

portapack-mayhem/firmware/chibios-portapack/ext/fatfs/src/ff.c: In function 'get_fat':
portapack-mayhem/firmware/chibios-portapack/ext/fatfs/src/ff.c:1038:7: warning: this statement may fall through [-Wimplicit-fallthrough=]
1038 | if (obj->objsize) {
| ^
portapack-mayhem/firmware/chibios-portapack/ext/fatfs/src/ff.c:1064:3: note: here
1064 | default:
| ^~~~~~~

[zxkmm]

Last time I didn't know if it should be fallthrough or not, so I tried both and both works I can't find difference.
Glad that you know and I trust your.

[gullradriel]

Indeed, both comment and attribute are working.

[zxkmm]

no i mean both break or fallthrough works. but glad to know it should be fallthrough

[gullradriel]

Ha, this.
There is a difference between break and fall through.
When you break, you go out of the switch directly.
When you fall through, you go to the next case, in our situation the default case was executed, so I kept it that way when adding the fall through flag.