arm64: dts: allwinner: a64: Olinuxino: fix DRAM voltage

The Olinuxino board uses DDR3L chips which are supposed to be driven
with 1.35V. The reset default of the AXP is properly set to 1.36V.

While technically the chips can also run at 1.5 volts, changing the
voltage on the fly while booting Linux is asking for trouble. Also
running at a lower voltage saves power.

So fix the DCDC5 value to match the actual board design.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Tested-by: Martin Lucina <martin@lucina.net>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Chen-Yu Tsai <wens@csie.org>