test: Use a local variable for test state

At present we use a global test state for all driver-model tests. Make use
of a local struct like we do with the other tests.

To make this work, add functions to get and set this state. When a test
starts, the state is set (so it can be used in the test). When a test
finishes, the state is unset, so it cannot be used by mistake.

Signed-off-by: Simon Glass <sjg@chromium.org>

include/test/ut.h

@@ -367,6 +367,20 @@ void ut_unsilence_console(struct unit_test_state *uts);
  */
 void ut_set_skip_delays(struct unit_test_state *uts, bool skip_delays);
 
+/**
+ * test_get_state() - Get the active test state
+ *
+ * @return the currently active test state, or NULL if none
+ */
+struct unit_test_state *test_get_state(void);
+
+/**
+ * test_set_state() - Set the active test state
+ *
+ * @uts: Test state to use as currently active test state, or NULL if none
+ */
+void test_set_state(struct unit_test_state *uts);
+
 /**
  * ut_run_test_live_flat() - Run a test with both live and flat tree
  *