scsi: mpt3sas: Remove flush_scheduled_work() call

It seems to me that mpt3sas driver is using dedicated workqueues and is not
calling schedule{,_delayed}_work{,_on}(). Then, there will be no work to
flush using flush_scheduled_work().

Link: https://lore.kernel.org/r/f3b97c7c-1094-4e46-20d8-4321716d6f3f@I-love.SAKURA.ne.jp


Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>