ARM: Add Gemini architecture v3

Adds support for Cortina Systems Gemini family CPUs:
http://www.cortina-systems.com/products/category/18



v3:
- fixed __io(a) to be defined as __typesafe_io(a)

v2:
- #include <asm/io.h> -> <linux/io.h>
- remove asm/system.h include
- revorked mm.c to use named initializers
- removed "empty" dma.h
- updated copyrights

Signed-off-by: Paulius Zaleckas <paulius.zaleckas@teltonika.lt>