tests: benchmarks: power_consumption: i2c: Improve thread suspend

Test thread cannot be suspended at any time because driver power
management happens in the thread context so if thread is suspended
at the random moment and system goes to s2ram it can lead to
increased power consumption because thread got suspended before
i2c device got properly suspended.

Signed-off-by: Krzysztof Chruściński <[email protected]>
(cherry picked from commit 4408403)

tests/benchmarks/power_consumption/i2c/src/driver_test.c

@@ -9,6 +9,13 @@
 
 static const struct device *i2c = DEVICE_DT_GET(DT_ALIAS(sensor_bme688));
 
+static bool suspend_req;
+
+bool self_suspend_req(void)
+{
+	suspend_req = true;
+	return true;
+}
 
 void thread_definition(void)
 {
@@ -17,6 +24,10 @@ void thread_definition(void)
 
 	while (1) {
 		ret = i2c_reg_read_byte(i2c, 0x76, 0x75, &value);
+		if (suspend_req) {
+			suspend_req = false;
+			k_thread_suspend(k_current_get());
+		}
 		if (ret < 0) {
 			printk("Failure in reading byte %d", ret);
 			return;