powerpc/b4860qds: Add support to dump switch settings on b4860qds board

This function is called by "qixis_reset switch" command
and switch settings are calculated from FPGA/qixis registers.

Signed-off-by: York Sun <yorksun@freescale.com>
Signed-off-by: Shaveta Leekha <shaveta@freescale.com>
Signed-off-by: Poonam Aggrwal <poonam.aggrwal@freescale.com>
Signed-off-by: Andy Fleming <afleming@freescale.com>