arm/dt: Add dt machine definition

This patch adds a DT_MACHINE_START macro to use instead of
MACHINE_START when creating a machine_desc that supports using the
device tree.
Signed-off-by: NGrant Likely <grant.likely@secretlab.ca>

arch/arm/include/asm/mach/arch.h

@@ -74,4 +74,11 @@ static const struct machine_desc __mach_desc_##_type	\
 #define MACHINE_END				\
 };
 
+#define DT_MACHINE_START(_name, _namestr)		\
+static const struct machine_desc __mach_desc_##_name	\
+ __used							\
+ __attribute__((__section__(".arch.info.init"))) = {	\
+	.nr		= ~0,				\
+	.name		= _namestr,
+
 #endif