sunxi: gpio: Add support for the gpio banks which are part of the R-io cluster

sunxi: gpio: Add support for the gpio banks which are part of the R-io cluster

sun6i and later have a couple of io-blocks which are shared between the
main CPU core and the "R" cpu which is small embedded cpu which can be
active while the main system is suspended.

These gpio banks sit at a different mmio address then the normal banks,
and have a separate devicetree node and compatible, this adds support for
these banks to the sunxi-gpio code when built with device-model support.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>