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>
diff --git a/test/dm/test-driver.c b/test/dm/test-driver.c
index 63dc9d3..02cb974 100644
--- a/test/dm/test-driver.c
+++ b/test/dm/test-driver.c
@@ -18,7 +18,6 @@
 #include <test/ut.h>
 
 int dm_testdrv_op_count[DM_TEST_OP_COUNT];
-static struct unit_test_state *uts = &global_dm_test_state;
 
 static int testdrv_ping(struct udevice *dev, int pingval, int *pingret)
 {
@@ -37,6 +36,8 @@
 
 static int test_bind(struct udevice *dev)
 {
+	struct unit_test_state *uts = test_get_state();
+
 	/* Private data should not be allocated */
 	ut_assert(!dev_get_priv(dev));
 
@@ -46,6 +47,7 @@
 
 static int test_probe(struct udevice *dev)
 {
+	struct unit_test_state *uts = test_get_state();
 	struct dm_test_priv *priv = dev_get_priv(dev);
 
 	/* Private data should be allocated */
@@ -58,6 +60,8 @@
 
 static int test_remove(struct udevice *dev)
 {
+	struct unit_test_state *uts = test_get_state();
+
 	/* Private data should still be allocated */
 	ut_assert(dev_get_priv(dev));
 
@@ -67,6 +71,8 @@
 
 static int test_unbind(struct udevice *dev)
 {
+	struct unit_test_state *uts = test_get_state();
+
 	/* Private data should not be allocated */
 	ut_assert(!dev_get_priv(dev));
 
@@ -116,6 +122,8 @@
 
 static int test_manual_probe(struct udevice *dev)
 {
+	struct unit_test_state *uts = test_get_state();
+
 	dm_testdrv_op_count[DM_TEST_OP_PROBE]++;
 	if (!uts->force_fail_alloc)
 		dev_set_priv(dev, calloc(1, sizeof(struct dm_test_priv)));