drm: Remove the ULONG_MAX stack trace hackery

No architecture terminates the stack trace with ULONG_MAX anymore. Remove
the cruft.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Alexander Potapenko <glider@google.com>
Cc: intel-gfx@lists.freedesktop.org
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: dri-devel@lists.freedesktop.org
Cc: David Airlie <airlied@linux.ie>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://lkml.kernel.org/r/20190410103644.945059666@linutronix.de

drivers/gpu/drm/drm_mm.c

@@ -113,9 +113,6 @@ static noinline void save_stack(struct drm_mm_node *node)
 	};
 
 	save_stack_trace(&trace);
-	if (trace.nr_entries != 0 &&
-	    trace.entries[trace.nr_entries-1] == ULONG_MAX)
-		trace.nr_entries--;
 
 	/* May be called under spinlock, so avoid sleeping */
 	node->stack = depot_save_stack(&trace, GFP_NOWAIT);

drivers/gpu/drm/i915/intel_runtime_pm.c

@@ -67,10 +67,6 @@ static noinline depot_stack_handle_t __save_depot_stack(void)
 	};
 
 	save_stack_trace(&trace);
-	if (trace.nr_entries &&
-	    trace.entries[trace.nr_entries - 1] == ULONG_MAX)
-		trace.nr_entries--;
-
 	return depot_save_stack(&trace, GFP_NOWAIT | __GFP_NOWARN);
 }