clk: at91: dt-compat: Hold reference returned by of_get_parent()

We need to hold the reference returned by of_get_parent() and use
it to call of_node_put() for refcount balance.
Signed-off-by: Liang He <windhl@126.com>
Link: https://lore.kernel.org/r/20220630143949.218922-1-windhl@126.comReviewed-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>