[POWERPC] MPC8641HPCN: Set IDE in ULI1575 to not native mode.

Set IDE in ULI1575 to not 100% native mode, which forces
the IDE driver to probe the irq itself.

Signed-off-by: Zhang Wei <wei.zhang@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>