ext4: delete declaration for ext4_split_extent()

There are no forward references for ext4_split_extent() in extents.c,
so delete its unnecessary declaration.
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Eric Whitney <enwlinux@gmail.com>
Link: https://lore.kernel.org/r/20200212162141.22381-1-enwlinux@gmail.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/extents.c

@@ -83,13 +83,6 @@ static void ext4_extent_block_csum_set(struct inode *inode,
 	et->et_checksum = ext4_extent_block_csum(inode, eh);
 }
 
-static int ext4_split_extent(handle_t *handle,
-				struct inode *inode,
-				struct ext4_ext_path **ppath,
-				struct ext4_map_blocks *map,
-				int split_flag,
-				int flags);
-
 static int ext4_split_extent_at(handle_t *handle,
 			     struct inode *inode,
 			     struct ext4_ext_path **ppath,