tests: spinlock: Increase thread execution to prevent quick exit

On Intel boards (like intel_ehl_crb and intel_rpl_s_crb) for the
trylock_test some part is executed very fast and since there is no
synchronization, there might be situation when there is no
trylock_failures. Increasing time spend in this part fixes the issue.

Signed-off-by: Andrei Emeltchenko <andrei.emeltchenko@intel.com>

tests/kernel/spinlock/src/main.c

@@ -97,8 +97,9 @@ void bounce_once(int id, bool trylock)
 	 */
 	bounce_owner = id;
 
-	for (i = 0; i < 100; i++) {
+	for (i = 0; i < 5; i++) {
 		zassert_true(bounce_owner == id, "Locked data changed");
+		k_busy_wait(1);
 	}
 
 	/* Release the lock */