msm_rq_stats: set rq_info.init after initializing rq_info attributes

It is possible the kobj not initialized before def_work_fn called.
Fix this by setting rq_info as initialized only after initializing
rq_info attributes.

Change-Id: Iff8c5c653b51c711a7ddc5bbeae8684fcbf2a742
Signed-off-by: Jin Hong <jinh@codeaurora.org>