Turn off the nand and dma clocks when we're done with the nand, this
puts the nand and dma controllers back into a clean state for when the
kernel boots.
Without this the kernel will not boot properly when it is built with
dma-controller support.
Signed-off-by: Hans de Goede <hdegoede@redhat.com> Acked-by: Ian Campbell <ijc@hellion.org.uk>