Revert RISC-V: sunset allwinner kernel flavour

According to the kernel team the Linux Meta package linux-allwinner shall
continue to be supplied. It will depend on generic packages.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>

live-build/auto/config

@@ -1131,6 +1131,9 @@ case $PROJECT in
 			riscv64*)
 				if [ -n "$SUBARCH" ]; then
 					case "${SUBARCH:-}" in
+						nezha|licheerv)
+							KERNEL_FLAVOURS=allwinner
+							;;
 						visionfive)
 							KERNEL_FLAVOURS=starfive
 							;;