openocd: remove NULL comparisons with checkpatch [1/2]

Patch generated automatically through the new checkpatch with
flags "--types COMPARISON_TO_NULL --fix-inplace".
This only fixes the comparisons
	if (symbol == NULL)
	if (symbol != NULL)
The case of NULL on the left side of the comparison is not tested.

Some automatic fix is incorrect and has been massaged by hands:
	-	if (*psig == NULL)
	+	if (*!psig)
changed as
	+	if (!*psig)

Change-Id: If4a1e2b4e547e223532e8e3d9da89bf9cb382ce6
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: http://openocd.zylin.com/6351
Tested-by: jenkins

src/rtos/linux.c

@@ -639,7 +639,7 @@ static struct threads *liste_add_task(struct threads *task_list, struct threads
 {
 	t->next = NULL;
 
-	if (*last == NULL)
+	if (!*last)
 		if (!task_list) {
 			task_list = t;
 			return task_list;