[ARM] 5280/1: pxa: prepare cm-x2xx.c and cm-x2xx-pci.[ch] for addition of CM-X255

- Change CM-X255 and CM-X270 common function prefix from cmx270 to cmx2xx
- Split cmx2xx_init to common and CM-X270-specific parts
- Use dynamic assignement for DM9000 resources and led GPIOs.

Signed-off-by: Russ Dill <russ.dill@gmail.com>
Signed-off-by: Mike Rapoport <mike@compulab.co.il>
Acked-by: Eric Miao <eric.miao@marvell.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>