siimage: fix kernel oops on PPC 44x

Fix kernel oops due to machine check occuring in init_chipset_siimage() on PPC
44x platforms.  These 32-bit CPUs have 36-bit physical address and PCI I/O and
memory spaces are mapped beyond 4 GB; arch/ppc/ code has a fixup in ioremap()
that creates an illusion of the PCI I/O and memory resources being mapped below
4 GB, while arch/powerpc/ code got rid of this fixup with PPC 44x having instead
CONFIG_RESOURCES_64BIT=y -- this causes the resources to be truncated to 32-bit
'unsigned long' type in this driver, and so non-existant memory being ioremap'ed
and then accessed...

Thanks to Valentine Barshak for providing an initial patch and explanations.

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>