ARM: sun6i: Use CPU_METHOD_OF_DECLARE

CPU_METHOD_OF_DECLARE allows to bind the smp_ops to a set of cpus through the
enable-method property, instead of relying on the machine to define it. Switch
to it to get closer to an empty machine.
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

arch/arm/mach-sunxi/platsmp.c

@@ -122,3 +122,4 @@ struct smp_operations sun6i_smp_ops __initdata = {
 	.smp_prepare_cpus	= sun6i_smp_prepare_cpus,
 	.smp_boot_secondary	= sun6i_smp_boot_secondary,
 };
+CPU_METHOD_OF_DECLARE(sun6i_smp, "allwinner,sun6i-a31", &sun6i_smp_ops);