dt-bindings: Rename the description of cpu nodes cpu.yaml

maillist inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I7ZC0H

Reference: https://lore.kernel.org/all/20211015161416.2196-1-james.morse@arm.com/t/#u



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The cpus.yaml file describes the cpu nodes, not the cpus node.
Rename it to allow integration properties of all the cpus to be described
in the cpus node.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ma Wupeng <mawupeng1@huawei.com>