PCI/P2PDMA: Use correct calc_map_type_and_dist() return type

Instead of using an int for the return value of this function, use the
correct enum pci_p2pdma_map_type.

Link: https://lore.kernel.org/r/20210610160609.28447-4-logang@deltatee.com


Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>