Add support for "4G Systems MTX-1 Flash device", better known as meshcube.

From: Bruno Randolf <bruno.randolf@4g-systems.biz>
Signed-off-by: NJoern Engel <joern@wohnheim.fh-wedel.de>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>