PCI: versatile: Remove usage of PHYS_OFFSET

PHYS_OFFSET is not universally defined on all arches and using it prevents
enabling COMPILE_TEST. PAGE_OFFSET and __pa() are always available, so use
them to get the physical start of memory address.

This should have probably used 'dma-ranges' to get the address, but we
don't want to force a DT update to do that. At least in QEMU, the SMAP
registers have no effect (or perhaps the only value that is handled is 0).

Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Andrew Murray <andrew.murray@arm.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>