RISC-V: handle kernel flavour allwinner

Package linux-allwinner has a kernel with the generic flavour as
dependency. Add this translation to our code checking the correct
installation.

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

live-build/auto/build

@@ -614,7 +614,7 @@ for FLAVOUR in $LB_LINUX_FLAVOURS; do
 		continue
 	fi
 	case $FLAVOUR in
-		virtual|generic-hwe-*)
+		allwinner|virtual|generic-hwe-*)
 			FLAVOUR="generic"
 			;;
 		oem-*)