ARM/net: ixp4xx: Pass ethernet physical base as resource

In order to probe this ethernet interface from the device tree
all physical MMIO regions must be passed as resources. Begin
this rewrite by first passing the port base address as a
resource for all platforms using this driver, remap it in
the driver and avoid using any reference of the statically
mapped virtual address in the driver.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>