clk: qcom: lcc-ipq806x: use ARRAY_SIZE for num_parents

Use ARRAY_SIZE for num_parents instead of raw number to prevent any
confusion/mistake.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20220724182329.9891-4-ansuelsmth@gmail.com