drm/i915: Extend hangcheck timeout

... reduce the frequency of checking to further reduce the wakeups and
CPU overhead.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/i915_drv.h

@@ -315,7 +315,7 @@ typedef struct drm_i915_private {
 	int num_pipe;
 
 	/* For hangcheck timer */
-#define DRM_I915_HANGCHECK_PERIOD 250 /* in ms */
+#define DRM_I915_HANGCHECK_PERIOD 1500 /* in ms */
 	struct timer_list hangcheck_timer;
 	int hangcheck_count;
 	uint32_t last_acthd;