[POWERPC] 4xx: Use dcri_clrset() for PCIe indirect dcr read/modify/write access

Use dcri_clrset() for PCIe SDR0 read/modify/write access.

Signed-off-by: Valentine Barshak <vbarshak@ru.mvista.com>
Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>