mips: dts: ingenic: Remove unnecessary AIC clocks

The "ext" and "pll half" clocks don't belong in the DT. They are
not consumed directly by the AIC and are only used as the parent
clocks of the "i2s" clock. An operating system should be able to
figure out that information itself because it presumably knows the
layout of the clock tree.

Removing these from the DT should be safe from a compatibility
point of view because the jz4740-i2s driver in Linux does not, and
never did depend on them.

Signed-off-by: Aidan MacDonald <aidanmacdonald.0x0@gmail.com>
Link: https://lore.kernel.org/all/20221028103418.17578-1-aidanmacdonald.0x0@gmail.com/
Reviewed-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>