ubuntu-cpc: install grub-efi on riscv images

grub-efi-riscv64 is in the archive and edk2 support for riscv is being
merged upstream.

live-build/ubuntu-cpc/hooks.d/base/disk-image-uefi.binary

@@ -268,7 +268,6 @@ install_grub() {
             fi
             ;;
         riscv64)
-            # TODO grub-efi-riscv64 exists, but is not used by all the images yet
             if [ -n "${SUBARCH:-}" ]; then
                 # Per-device images
                 local my_d=$(dirname $(readlink -f ${0}))
@@ -451,7 +450,7 @@ EOF
                 esac
             else
                 # Other images e.g. cloud images
-                chroot mountpoint apt-get install -qqy u-boot-menu #grub-efi-riscv64
+                chroot mountpoint apt-get install -qqy u-boot-menu grub-efi-riscv64
                 efi_target=riscv64-efi
 
                 chroot mountpoint u-boot-update