kunit: test.h: fix format string for ASSERT_NOT_ERR_OR_NULL

davidchiang@ pointed out the format string differs from
EXPECT_NOT_ERR_OR_NULL.

The latter correctly uses %s while this uses %ld, producing stuff like
> Asserted ptr is not error, but is: 1887632768
This was missed in 1304e037936b2 which added the strerror_r() call.

Fixing that, the two macros are again identical in all the ways we expect.

Change-Id: I8af8e5ba2770e92f8d4fe1967091256f2c74a252
Signed-off-by: Daniel Latypov <dlatypov@google.com>
diff --git a/include/test/test.h b/include/test/test.h
index 1369963..755baf8 100644
--- a/include/test/test.h
+++ b/include/test/test.h
@@ -942,7 +942,7 @@
 			      "Asserted " #ptr " is not null, but is.");       \
 	if (IS_ERR(__ptr))						       \
 		__stream->add(__stream,					       \
-			      "Asserted " #ptr " is not error, but is: %ld",   \
+			      "Asserted " #ptr " is not error, but is: %s",   \
 			      strerror_r(-PTR_ERR(__ptr), buf, sizeof(buf)));  \
 									       \
 	ASSERT_END(test, !IS_ERR_OR_NULL(__ptr), __stream);		       \