dt-bindings: arm: cpus: Add Kryo 250 CPUs

Document Kryo 250 CPUs found in Qualcomm Snapdragon 632 (SDM632).

Signed-off-by: Luca Weiss <luca@z3ntu.xyz>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20220220201909.445468-5-luca@z3ntu.xyz