clk: samsung: exynos5433: Use of_clk_get_parent_count()

Use of_clk_get_parent_count() instead of open coding.

Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Acked-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>