ARM: pxa: dts: add pin definitions for extended GPIOs

The PXA3xx series features some extended GPIO banks which are named GPIO0_2,
GPIO1_2 etc. The PXA300, PXA310 and PXA320 have different numbers of such
pins, and they also have variant-specific register offsets.

Signed-off-by: Daniel Mack <daniel@zonque.org>
Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>