palm_bk3710: improve IDE registration

* fix device tree ... don't forget to set the parent device

* let init/exit code be removed where practical

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
[bart: splitted it from bigger DaVinci patch, s/hw.parent/hw.dev/]
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>