ide-floppy: add ide_floppy_format_ioctl() helper

* Factor out IDEFLOPPY_IOCTL_FORMAT_* ioctls handling from
  idefloppy_ioctl() to ide_floppy_format_ioctl().

While at it:

* Pass 'drive' instead of 'floppy' to ide_floppy_format_unit().

* idefloppy_get_format_progress() -> ide_floppy_get_format_progress()

There should be no functional changes caused by this patch.

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