ARM: mvebu: Move kirkwood DT boards into mach-mvebu

Move the kirkwood DT support into mach-mvebu, and make them part of
ARCH_MULTI_V5. Minimal changes have been made in order to make it
boot. Cleanup of the header files and integration with mvebu will
take place in following patches.

In order to help Debian transition between mach-kirkwood and
mach-mvebu, the DTS files are compiled for both, allowing Debian to
continue using mach-kirkwood until all remaining boards are supported
by mach-mvebu. Debian is then expected to simply swap from
mach-kirkwood to mach-mvebu and mach-kirkwood will be removed.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>