mach-shmobile: Use DT_MACHINE for KZM9D V3

Use DT_MACHINE_START() on the emev2 based KZM9D board.

Also include a tiny DTS file to describe the board and
update the Kconfig dependencies to select CONFIG_USE_OF.

Update the SMP glue code to use OF for matching.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>