clk: qcom: mmcc-msm8960: use ARRAY_SIZE instead of specifying num_parents

Use ARRAY_SIZE() instead of manually specifying num_parents. This makes
adding/removing entries to/from parent_data easy and errorproof.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Tested-by: David Heidelberg <david@ixit.cz> # tested on Nexus 7 (2013)
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20220623120418.250589-8-dmitry.baryshkov@linaro.org