[SCSI] scsi-ml: Makefile and Kconfig changes for tgt

Makefile and Kconfig for tgt.

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>