ARM: mach-shmobile: Use DT_MACHINE for mackerel

Use DT_MACHINE_START() on the sh7372 based mackerel board.

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

Signed-off-by: Nobuhiro Iwamatsu <nobuhiro.iwamatsu.yj@renesas.com>
Signed-off-by: Simon Horman <horms@verge.net.au>
diff --git a/arch/arm/mach-shmobile/Kconfig b/arch/arm/mach-shmobile/Kconfig
index 8ae100c..0750d9c 100644
--- a/arch/arm/mach-shmobile/Kconfig
+++ b/arch/arm/mach-shmobile/Kconfig
@@ -95,6 +95,7 @@
 	select ARCH_REQUIRE_GPIOLIB
 	select REGULATOR_FIXED_VOLTAGE if REGULATOR
 	select SND_SOC_AK4642 if SND_SIMPLE_CARD
+	select USE_OF
 
 config MACH_KOTA2
 	bool "KOTA2 board"