powerpc/qe: Increase MAX_QE_RISC to 4

MPC8569 CPUs have four QE RISCs, so we need to increase MAX_QE_RISC
constant, otherwise qe_upload_firmware() fails at sanity checking.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Acked-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>