PM / devfreq: exynos-ppmu: Fix excessive stack usage

Putting a 'struct devfreq_event_dev' object on the stack is generally
a bad idea and here it leads to a warnig about potential stack overflow:

drivers/devfreq/event/exynos-ppmu.c:643:12: error: stack frame size of 1040 bytes in function 'exynos_ppmu_probe' [-Werror,-Wframe-larger-than=]

There is no real need for the device structure, only the string inside
it, so add an internal helper function that simply takes the string
as its argument and remove the device structure.

Fixes: 1dd62c66 ("PM / devfreq: events: extend events by type of counted data")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
[cw00.choi: Fix the issue from 'desc->name' to 'desc[j].name']
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>

drivers/devfreq/event/exynos-ppmu.c

@@ -101,17 +101,22 @@ static struct __exynos_ppmu_events {
 	PPMU_EVENT(dmc1_1),
 };
 
-static int exynos_ppmu_find_ppmu_id(struct devfreq_event_dev *edev)
+static int __exynos_ppmu_find_ppmu_id(const char *edev_name)
 {
 	int i;
 
 	for (i = 0; i < ARRAY_SIZE(ppmu_events); i++)
-		if (!strcmp(edev->desc->name, ppmu_events[i].name))
+		if (!strcmp(edev_name, ppmu_events[i].name))
 			return ppmu_events[i].id;
 
 	return -EINVAL;
 }
 
+static int exynos_ppmu_find_ppmu_id(struct devfreq_event_dev *edev)
+{
+	return __exynos_ppmu_find_ppmu_id(edev->desc->name);
+}
+
 /*
  * The devfreq-event ops structure for PPMU v1.1
  */
@@ -556,13 +561,11 @@ static int of_get_devfreq_events(struct device_node *np,
 			 * use default if not.
 			 */
 			if (info->ppmu_type == EXYNOS_TYPE_PPMU_V2) {
-				struct devfreq_event_dev edev;
 				int id;
 				/* Not all registers take the same value for
 				 * read+write data count.
 				 */
-				edev.desc = &desc[j];
-				id = exynos_ppmu_find_ppmu_id(&edev);
+				id = __exynos_ppmu_find_ppmu_id(desc[j].name);
 
 				switch (id) {
 				case PPMU_PMNCNT0: