km-arm: i2c support for suenx based boards

This patch renames the suen3 defines and functions to KM_KIRKWOOD
which is more generic and more precise, because these values
and functions where used by all suenX boards and not only suen3.

Signed-off-by: Lukas Roggli <lukas.roggli@keymile.com>
Signed-off-by: Valentin Longchamp <valentin.longchamp@keymile.com>
Signed-off-by: Holger Brunck <holger.brunck@keymile.com>
Signed-off-by: Heiko Schocher <hs@denx.de>
cc: Prafulla Wadaskar <prafulla@marvell.com>