rng: msm: keep core clock disabled when PRNG not in use

rng: msm: keep core clock disabled when PRNG not in use

This is how the kernel does it. APQ8016E TRM also states that this clock
can be turned off when no random numbers are needed.

Signed-off-by: Sam Day <me@samcday.com>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Reviewed-by: Caleb Connolly <caleb.connolly@linaro.org>
Link: https://lore.kernel.org/r/20250212-msm-rng-fixes-v2-5-645cf8d3fd3c@samcday.com
Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>