ARM: dts: qcom: mdm9615: drop second clock frequency from timer

Keep only one clock frequency for timer, because:
1. DT schema does not allow multiple frequencies in such property,
2. The Linux timer driver reads only first frequency.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20221212163532.142533-10-krzysztof.kozlowski@linaro.org