The patch "reduce repetitive calculation of max number of child nodes"
gathered up the calculation of maximum number of child nodes into
nilfs_btree_nchildren_per_block() function.  This makes the function
get resultant value from a private variable in bmap object instead of
calculating it for each call.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>