clk: samsung: Extract parent clock enabling to common function

Extract parent clock enabling from exynos_arm64_register_cmu() to
dedicated function.

Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Link: https://lore.kernel.org/r/20230307002423.24454-3-semen.protsenko@linaro.org


Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>