tgt: defconfig cleanup

Because of the removal of the scsi_tgt kernel module, the kbuild variables
CONFIG_SCSI_TGT, CONFIG_SCSI_SRP_TGT_ATTRS and CONFIG_SCSI_FC_TGT_ATTRS
are obsolete. This patch removes these variables. This patch is the result
of the following command:

find -name '*defconfig' | while read f; do grep -vwE 'CONFIG_SCSI_TGT|CONFIG_SCSI_SRP_TGT_ATTRS|CONFIG_SCSI_FC_TGT_ATTRS|CONFIG_SRP' $f >/tmp/t && mv /tmp/t $f; done

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>