btrfs: rename setup_extent_mapping in relocation code

In btrfs code we have two functions called setup_extent_mapping, one in
the extent_map code and one in the relocation code. While both are
private to their respective implementation, this can still be confusing
for the reader.

So rename the version in relocation.c to setup_relocation_extent_mapping.
No functional changes.
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/relocation.c

@@ -2879,9 +2879,8 @@ static noinline_for_stack int prealloc_file_extent_cluster(
 	return ret;
 }
 
-static noinline_for_stack
-int setup_extent_mapping(struct inode *inode, u64 start, u64 end,
-			 u64 block_start)
+static noinline_for_stack int setup_relocation_extent_mapping(struct inode *inode,
+				u64 start, u64 end, u64 block_start)
 {
 	struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
 	struct extent_map *em;
@@ -3080,7 +3079,7 @@ static int relocate_file_extent_cluster(struct inode *inode,
 
 	file_ra_state_init(ra, inode->i_mapping);
 
-	ret = setup_extent_mapping(inode, cluster->start - offset,
+	ret = setup_relocation_extent_mapping(inode, cluster->start - offset,
 				   cluster->end - offset, cluster->start);
 	if (ret)
 		goto out;