ARM: dts: sun8i: tbs-a711: Fix typo in regulators

The regulator properties suffix is -supply, yet a _supply slipped in.

This was working because the regulator framework will provide a dummy
regulator when none is provided in the device tree, and the regulator
itself was always enabled.

Fixes: 90c5d7cd ("ARM: dts: sun8i: a711: Add regulator support")
Acked-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>