ide-floppy: move all ioctl handling to ide-floppy_ioctl.c (take 2)

While at it:
- idefloppy_ioctl() -> ide_floppy_ioctl()

v2:
Fix for idefloppy_ioctl name change from Stephen Rothwell.

Cc: Borislav Petkov <petkovbb@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>