floppy: Fix failed media sense return code

An error in floppy_media_sense() returned error code 0xc0.  However,
this appears to be a typo when porting the original bochs bios code,
as it uses 0x0c.  It appears this typo was introduced in the first
SeaBIOS commit (f076a3ee).

Change the code to return 0x0c (DISK_RET_EBADTRACK) on an error.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>