arm64: dts: allwinner: a64: Enable A64 timer workaround

As instability in the architectural timer has been observed on multiple
devices using this SoC, inluding the Pine64 and the Orange Pi Win,
enable the workaround in the SoC's device tree.

Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Chen-Yu Tsai <wens@csie.org>