clk: oxnas: Hold reference returned by of_get_parent()

clk: oxnas: Hold reference returned by of_get_parent()

In oxnas_stdclk_probe(), we need to hold the reference returned by
of_get_parent() and use it to call of_node_put() for refcount
balance.

Fixes: 0bbd72b4c64f ("clk: Add Oxford Semiconductor OXNAS Standard Clocks")
Signed-off-by: Liang He <windhl@126.com>
Link: https://lore.kernel.org/r/20220628143155.170550-1-windhl@126.com
Signed-off-by: Stephen Boyd <sboyd@kernel.org>