initfs: support for modloop boot option

initramfs-init

@@ -121,7 +121,12 @@ mount $mount_opts /dev/$ALPINE_DEV $ALPINE_MNT >/dev/null 2>&1
 eend $?
 ebegin "Mounting loopback device for kernel modules"
 modprobe loop
-mount -o loop,ro -t cramfs $ALPINE_MNT/$KOPT_BOOT_IMAGE.cmg /.modloop
+if [ -n "$KOPT_modloop" ]; then
+	modloop=$KOPT_modloop
+else
+	modloop=$KOPT_BOOT_IMAGE.cmg
+fi
+mount -o loop,ro -t cramfs $ALPINE_MNT/$modloop /.modloop
 rc=$?
 if [ "$rc" = 0 ]; then
 	rm -rf /lib/modules