btrfs: sink get_extent parameter to extent_write_full_page

There's only one caller.
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent_io.c

@@ -4058,14 +4058,13 @@ static noinline void flush_write_bio(void *data)
 }
 
 int extent_write_full_page(struct extent_io_tree *tree, struct page *page,
-			  get_extent_t *get_extent,
 			  struct writeback_control *wbc)
 {
 	int ret;
 	struct extent_page_data epd = {
 		.bio = NULL,
 		.tree = tree,
-		.get_extent = get_extent,
+		.get_extent = btrfs_get_extent,
 		.extent_locked = 0,
 		.sync_io = wbc->sync_mode == WB_SYNC_ALL,
 	};

fs/btrfs/extent_io.h

@@ -404,7 +404,6 @@ int find_first_extent_bit(struct extent_io_tree *tree, u64 start,
 int extent_invalidatepage(struct extent_io_tree *tree,
 			  struct page *page, unsigned long offset);
 int extent_write_full_page(struct extent_io_tree *tree, struct page *page,
-			  get_extent_t *get_extent,
 			  struct writeback_control *wbc);
 int extent_write_locked_range(struct extent_io_tree *tree, struct inode *inode,
 			      u64 start, u64 end, int mode);

fs/btrfs/inode.c

@@ -8891,7 +8891,7 @@ static int btrfs_writepage(struct page *page, struct writeback_control *wbc)
 		return AOP_WRITEPAGE_ACTIVATE;
 	}
 	tree = &BTRFS_I(page->mapping->host)->io_tree;
-	ret = extent_write_full_page(tree, page, btrfs_get_extent, wbc);
+	ret = extent_write_full_page(tree, page, wbc);
 	btrfs_add_delayed_iput(inode);
 	return ret;
 }