scsi: mpi3mr: Schedule IRQ kthreads only on non-RT kernels

In RT kernels, the IRQ handler's code is executed as a kernel
thread. Modify the driver to avoid explicitly scheduling the IRQ kernel
thread.

Link: https://lore.kernel.org/r/20220912135742.11764-4-sreekanth.reddy@broadcom.com


Signed-off-by: Sreekanth Reddy <sreekanth.reddy@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>