lib: remove unnecessary checks on the drm_open_any return value

drm_open_any always returns a valid file descriptor, so there is no need
to check the return value.

Signed-off-by: Thomas Wood <thomas.wood@intel.com>

lib/drmtest.c

@@ -302,10 +302,10 @@ static void quiescent_gpu_at_exit_render(int sig)
 /**
  * drm_open_any:
  *
- * Open an i915 drm legacy device node.
+ * Open an i915 drm legacy device node. This function always returns a valid
+ * file descriptor.
  *
- * Returns:
- * The i915 drm file descriptor or -1 on error
+ * Returns: a i915 drm file descriptor
  */
 int drm_open_any(void)
 {

lib/igt.cocci

@@ -127,3 +127,17 @@ expression b;
 - ((a) >= (b) ? (a) : (b))
 + max(a, b)
 )
+
+// drm_open_any always returns a valid file descriptor
+@@
+expression a;
+@@
+a = drm_open_any();
+(
+- igt_assert(a >= 0);
+|
+- if (a < 0) {
+- ...
+- return ...;
+- }
+)