ARM: dts: spear320: Drop unused and undocumented 'irq-over-gpio' property

The property 'irq-over-gpio' is both unused and undocumented. It also
happens to collide with standard *-gpio properties. As it is not needed,
drop it.

Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220204004117.1232902-1-robh@kernel.org

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Signed-off-by: Arnd Bergmann <arnd@arndb.de>