clk: get matching entry under lock in of_clk_init()

Currently of_clk_init() finds a matching device node while holding
the device tree spinlock.  When a matching device node is found, the
lock is dropped and then re-acquired in order to get a reference
to the matching device id structure.

Acquiring the spinlock twice is unnecessary (and it opens a
vulnerable window that could conceivably lead to errors).

There already exists an interface for both finding and taking a
reference to a device id under lock, so use it.

Signed-off-by: Alex Elder <elder@linaro.org>
Reviewed-by: Christian Daudt <csd@broadcom.com>
Reviewed-by: Markus Mayer <markus.mayer@linaro.org>
Reviewed-by: Matt Porter <matt.porter@linaro.org>
Signed-off-by: Mike Turquette <mturquette@linaro.org>

drivers/clk/clk.c

@@ -2228,13 +2228,13 @@ EXPORT_SYMBOL_GPL(of_clk_get_parent_name);
  */
 void __init of_clk_init(const struct of_device_id *matches)
 {
+	const struct of_device_id *match;
 	struct device_node *np;
 
 	if (!matches)
 		matches = __clk_of_table;
 
-	for_each_matching_node(np, matches) {
-		const struct of_device_id *match = of_match_node(matches, np);
+	for_each_matching_node_and_match(np, matches, &match) {
 		of_clk_init_cb_t clk_init_cb = match->data;
 		clk_init_cb(np);
 	}