powerpc/scom: Enable 64-bit addresses

On P8, XSCOM addresses has a special "indirect" form that
requires more than 32-bits, so let's use u64 everywhere in
the code instead of u32.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

diff --cc arch/powerpc/include/asm/scom.h
Simple merge

diff --cc arch/powerpc/platforms/powernv/opal-xscom.c
Simple merge

diff --cc arch/powerpc/platforms/wsp/scom_wsp.c
Simple merge