[SCSI] mpt2sas: removed use of tm_cmds.mutex in IOCTL branch.

Removed all the mutex's for ioc->tm_cmds.mutex, then created one
single mutex inside the function mpt2sas_scsih_issue_tm. This is the
single function used when sending task management. Also the sanity
checks required for scsi mid layer escalation were moved to inside the
same function because these checks need to be done while the mutex is
held. The ioc->tm_cmds.mutex inside the IOCTL branch is really not
required since there is another mutex in this code called for ctl_cmds
handling this sync.

Signed-off-by: Kashyap Desai <kashyap.desai@lsi.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>