clocksource/drivers/integrator-ap: Add missing of_node_put()

The function of_find_node_by_path() acquires a reference to the node
returned by it and that reference needs to be dropped by its caller.

integrator_ap_timer_init_of() doesn't do that.  The pri_node and the
sec_node are used as an identifier to compare against the current
node, so we can directly drop the refcount after getting the node from
the path as it is not used as pointer.

By dropping the refcount right after getting it, a single variable is
needed instead of two.

Fix this by use a single variable and drop the refcount right after
of_find_node_by_path().

Signed-off-by: Yangtao Li <tiny.windzz@gmail.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>