samples: boards: nordic: coresight_stm: Improve benchmark

Add interrupt locking during test to ensure that main thread is not
interrupts which would impact the test.

Add longer sleep time between tests to ensure that all logs are
processed on time and not dropped.

(cherry picked from commit c61e92a)

Original-Signed-off-by: Krzysztof Chruściński <krzysztof.chruscinski@nordicsemi.no>
GitOrigin-RevId: c61e92a
Cr-Build-Id: 8735619482632649473
Cr-Build-Url: https://cr-buildbucket.appspot.com/build/8735619482632649473
Copybot-Job-Name: zephyr-main-copybot-downstream
Change-Id: I136adbe43562fdd914485da1c53272c58e4df046
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/zephyr/+/5896230
Reviewed-by: Fabio Baltieri <fabiobaltieri@google.com>
Commit-Queue: Fabio Baltieri <fabiobaltieri@google.com>
Tested-by: ChromeOS Prod (Robot) <chromeos-ci-prod@chromeos-bot.iam.gserviceaccount.com>
Tested-by: Fabio Baltieri <fabiobaltieri@google.com>

samples/boards/nordic/coresight_stm/src/main.c

@@ -16,12 +16,14 @@ LOG_MODULE_REGISTER(app);
 
 #define TEST_LOG(rpt, item)                                                                        \
 	({                                                                                         \
+		uint32_t key = irq_lock();                                                         \
 		uint32_t t = k_cycle_get_32();                                                     \
 		for (uint32_t i = 0; i < rpt; i++) {                                               \
 			__DEBRACKET item;                                                          \
 		}                                                                                  \
 		t = k_cycle_get_32() - t;                                                          \
-		k_msleep(200);                                                                     \
+		irq_unlock(key);                                                                   \
+		k_msleep(400);                                                                     \
 		t;                                                                                 \
 	})