clk: samsung: exynos4: fix refcount leak in exynos4_get_xom()

The of_find_compatible_node() returns a node pointer with refcount
incremented, but there is the lack of use of the of_node_put() when
done. Add the missing of_node_put() to release the refcount.

Signed-off-by: Yangtao Li <tiny.windzz@gmail.com>
Fixes: e062b571 ("clk: exynos4: register clocks using common clock framework")
Signed-off-by: Stephen Boyd <sboyd@kernel.org>