amifd.h and amifdreg.h are only used from amiflop.c, and they're pretty
small, so move the contents to amiflop.c and get rid of the .h files.
This is preparation for adding a struct blk_mq_tag_set to struct
amiga_floppy_struct.
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>