sam460ex: Update u-boot-sam460ex firmware

Update the submodule and u-boot-sam460-20100605.bin to include
following fixes from Sebastian Bauer:
- Fix build with newer gcc
- Decrease unnecessary delay which fixes slow booting from CD

Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>