dma-buf/sw_sync: mark sync_timeline_create() static

We get 1 warning when building kernel with W=1:
drivers/dma-buf/sw_sync.c:87:23: warning: no previous prototype for 'sync_timeline_create' [-Wmissing-prototypes]

In fact, this function is only used in the file in which it is
declared and don't need a declaration, but can be made static.
So this patch marks it 'static'.
Signed-off-by: Baoyou Xie <baoyou.xie@linaro.org>
Reviewed-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>
Link: http://patchwork.freedesktop.org/patch/msgid/1474202961-10099-1-git-send-email-baoyou.xie@linaro.org

drivers/dma-buf/sw_sync.c

@@ -84,7 +84,7 @@ static inline struct sync_pt *dma_fence_to_sync_pt(struct dma_fence *fence)
  * Creates a new sync_timeline. Returns the sync_timeline object or NULL in
  * case of error.
  */
-struct sync_timeline *sync_timeline_create(const char *name)
+static struct sync_timeline *sync_timeline_create(const char *name)
 {
 	struct sync_timeline *obj;