CFQ: move think time check variables to a separate struct

Move the variables to do think time check to a sepatate struct. This is
to prepare adding think time check for service tree and group. No
functional change.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

diff --cc block/cfq-iosched.c
Simple merge

diff --cc include/linux/iocontext.h
Simple merge