scsi: MAINTAINERS: SCSI initiator and target tweaks

Nic has been absent for a while and target changes now go through the SCSI
tree. To avoid confusion wrt. the NVMe target, clarify that this entry
refers to the SCSI target subsystem.

Also add patchwork links for both SCSI initiator and target.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>