The device_node pointer returned by of_find_compatible_node() with
refcount incremented, when finish using it, the refcount need be
decreased.

Fixes: d7964de8 ("clk: mediatek: Add new clock driver to handle FHCTL hardware")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20221229092946.4162345-1-yangyingliang@huawei.com
[sboyd@kernel.org: Also unmap on error]
Signed-off-by: Stephen Boyd <sboyd@kernel.org>