compat_ioctl: ide: floppy: add handler

Rather than relying on fs/compat_ioctl.c, this adds support
for a compat_ioctl() callback in the ide-floppy driver directly,
which lets it translate the scsi commands.

Reviewed-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>