include generic.ins for s390 boot iso

Include the generic.ins file on the s390 boot iso, so it's directly bootable
on an LPAR. The full iso already had generic.ins included.

Signed-off-by: Brian C. Lane <bcl@redhat.com>

Resolves: rhbz#1844517

80-rhel/s390.tmpl

@@ -71,6 +71,7 @@ runcmd mkisofs -o ${outroot}/images/boot.iso \
        -b ${BOOTDIR}/cdboot.img -c ${BOOTDIR}/boot.cat \
        -boot-load-size 4 -no-emul-boot \
        -R -J -V '${isolabel}' -T -graft-points \
+       generic.ins=${outroot}/generic.ins \
        ${BOOTDIR}=${outroot}/${BOOTDIR} \
        ${filegraft}
 treeinfo images-${basearch} boot.iso images/boot.iso