ok3e: Add ICSWX/ACOP support to Book3e cores like A2

ICSWX is also used by the A2 processor to access coprocessors,
although not all "chips" that contain A2s have coprocessors.

Signed-off-by: Jimi Xenidis <jimix@pobox.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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