ARM: sun9i: smp: Rename clusters's power-off

To prepare the support for sun8i-a83t, rename the macro that handles
the power-off of clusters because it is different from sun9i-a80 to
sun8i-a83t.

The power off register for clusters are different from a80 and a83t.

Signed-off-by: Mylène Josserand <mylene.josserand@bootlin.com>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>