arm64: dts: qcom: sm8250: use the right clock-freqency for sleep-clk

Downstream has this clock as 32000 rate, but testing shows it is close to
32768.

Signed-off-by: Jonathan Marek <jonathan@marek.ca>
Link: https://lore.kernel.org/r/20200903215923.14314-1-jonathan@marek.ca


Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>