RISC-V: rename cmdline.cfg to 10_cmdline.cfg

Using numbered configuration fragments makes the order of application
easier to track

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

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

@@ -243,7 +243,7 @@ install_grub() {
                 local my_d=$(dirname $(readlink -f ${0}))
                 echo "Adjusting GRUB defaults for ${ARCH}"
                 mkdir -p mountpoint/etc/default/grub.d/
-                cp ${my_d}/riscv64/grub/cmdline.cfg mountpoint/etc/default/grub.d/
+                cp ${my_d}/riscv64/grub/10_cmdline.cfg mountpoint/etc/default/grub.d/
                 case "${SUBARCH}" in
                     "icicle")
                         echo "Installing GRUB for ${SUBARCH} board"