powerpc/85xx: Fix booting for P1021MDS boards

P1021 processors have no dedicated ROM to store the QE microcode,
so the fimrware is stored externally, and it is U-Boot responsibility
to load it. It might be that the board is booting without QE, e.g.
currently U-Boot doesn't support QE for P1021MDS boards, which means
that QE isn't initialized, and so the board hangs early at boot.

This patch fixes the issue by marking QE as disabled and checking the
state in the probing code. U-Boot should fixup the state if it
initialized the QE.

Signed-off-by: Anton Vorontsov <avorontsov@mvista.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>