[SCSI] mpt2sas: LUN Reset Support

Adding new eh_target_reset_handler for target reset. Change the
eh_device_reset_handler so its sending
MPI2_SCSITASKMGMT_TASKTYPE_LOGICAL_UNIT_RESET, instead of
MPI2_SCSITASKMGMT_TASKTYPE_TARGET_RESET.  Add new function
_scsih_scsi_lookup_find_by_lun as a sanity check to insure I_T_L commands are
completed upon completing lun reset.

Signed-off-by: Eric Moore <eric.moore@lsi.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>