drm/ttm: Remove needless 'extern' on functions in header.

Minor tidy up.
Signed-off-by: Tom St Denis <tom.stdenis@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

include/drm/ttm/ttm_page_alloc.h

@@ -47,7 +47,7 @@ void ttm_page_alloc_fini(void);
  *
  * Add backing pages to all of @ttm
  */
-extern int ttm_pool_populate(struct ttm_tt *ttm);
+int ttm_pool_populate(struct ttm_tt *ttm);
 
 /**
  * ttm_pool_unpopulate:
@@ -56,12 +56,12 @@ extern int ttm_pool_populate(struct ttm_tt *ttm);
  *
  * Free all pages of @ttm
  */
-extern void ttm_pool_unpopulate(struct ttm_tt *ttm);
+void ttm_pool_unpopulate(struct ttm_tt *ttm);
 
 /**
  * Output the state of pools to debugfs file
  */
-extern int ttm_page_alloc_debugfs(struct seq_file *m, void *data);
+int ttm_page_alloc_debugfs(struct seq_file *m, void *data);
 
 
 #if defined(CONFIG_SWIOTLB) || defined(CONFIG_INTEL_IOMMU)
@@ -78,10 +78,10 @@ void ttm_dma_page_alloc_fini(void);
 /**
  * Output the state of pools to debugfs file
  */
-extern int ttm_dma_page_alloc_debugfs(struct seq_file *m, void *data);
+int ttm_dma_page_alloc_debugfs(struct seq_file *m, void *data);
 
-extern int ttm_dma_populate(struct ttm_dma_tt *ttm_dma, struct device *dev);
-extern void ttm_dma_unpopulate(struct ttm_dma_tt *ttm_dma, struct device *dev);
+int ttm_dma_populate(struct ttm_dma_tt *ttm_dma, struct device *dev);
+void ttm_dma_unpopulate(struct ttm_dma_tt *ttm_dma, struct device *dev);
 
 
 /**