arm64: dts: allwinner: a64: Fix up RTC device node and clock references

The RTC module on the A64 was claimed to be the same as on the A31, when
in fact it is not. It is actually compatible to the H3's RTC. The A64's
RTC has some extra crypto-related registers which the H3's does not, but
the exact function of these is not clear.

This patch fixes the compatible string and clock properties to conform
to the updated bindings. The device node for the internal oscillator is
removed, as it is internalized into the RTC device. Clock references to
the IOSC and LOSC are also fixed.

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