tj: dropped iff -> if, iff is if and only if not a typo.  Spotted by
    Randy Dunlap.
Signed-off-by: NShailendra Verma <shailendra.capricorn@gmail.com>
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>