drm: Fix conflicting macro parameter in drm_mm_for_each_node_in_range()

start is being used as both a macro parameter and as a member of struct
drm_mm_node (node->start). This causes a conflict as cpp then tries to
replace node->start with the passed in string for "start". Work just
fine so long as you also happened to using local variables called start!

Fixes: 522e85dd ("drm: Define drm_mm_for_each_node_in_range()")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Christian König <christian.koenig@amd.com>.
[danvet: Fixup kerneldoc.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20161127111623.11124-1-chris@chris-wilson.co.uk

include/drm/drm_mm.h

@@ -313,10 +313,10 @@ __drm_mm_interval_first(struct drm_mm *mm, u64 start, u64 last);
 /**
  * drm_mm_for_each_node_in_range - iterator to walk over a range of
  * allocated nodes
- * @node: drm_mm_node structure to assign to in each iteration step
- * @mm: drm_mm allocator to walk
- * @start: starting offset, the first node will overlap this
- * @end: ending offset, the last node will start before this (but may overlap)
+ * @node__: drm_mm_node structure to assign to in each iteration step
+ * @mm__: drm_mm allocator to walk
+ * @start__: starting offset, the first node will overlap this
+ * @end__: ending offset, the last node will start before this (but may overlap)
  *
  * This iterator walks over all nodes in the range allocator that lie
  * between @start and @end. It is implemented similarly to list_for_each(),
@@ -324,10 +324,10 @@ __drm_mm_interval_first(struct drm_mm *mm, u64 start, u64 last);
  * starting node, and so not safe against removal of elements. It assumes
  * that @end is within (or is the upper limit of) the drm_mm allocator.
  */
-#define drm_mm_for_each_node_in_range(node, mm, start, end)		\
-	for (node = __drm_mm_interval_first((mm), (start), (end)-1);	\
-	     node && node->start < (end);				\
-	     node = list_next_entry(node, node_list))			\
+#define drm_mm_for_each_node_in_range(node__, mm__, start__, end__)	\
+	for (node__ = __drm_mm_interval_first((mm__), (start__), (end__)-1); \
+	     node__ && node__->start < (end__);				\
+	     node__ = list_next_entry(node__, node_list))
 
 void drm_mm_init_scan(struct drm_mm *mm,
 		      u64 size,