s390/pci: store DMA offset in bus_dma_region

s390/pci: store DMA offset in bus_dma_region

PCI devices on s390 have a DMA offset that is reported via CLP.  In
preparation for allowing identity domains, setup the bus_dma_region
for all PCI devices using the reported CLP value.

Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com>
Tested-by: Niklas Schnelle <schnelle@linux.ibm.com>
Link: https://lore.kernel.org/r/20250212213418.182902-3-mjrosato@linux.ibm.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>