ARM: dts: kirkwood: add kirkwood-km_common DTSI files

This file allows to factor the common parts between the various Keymile
Kirkwood Designs.

kirkwood-km_common configures the peripherals that are currently
common to all our Kirkwood designs: PCIe, pinctrl, bitbang I2C, NAND
Flash controller.

The kirkwood-km_kirkwood file is then changed to include this common
file.

Signed-off-by: Valentin Longchamp <valentin.longchamp@keymile.com>
Link: https://lkml.kernel.org/r/1400230143-15620-3-git-send-email-valentin.longchamp@keymile.com


Acked-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>