RISC-V: avoid soft lockup Radeon GPUs with GRUB

With Radeon GPUs and kernel 5.19 a soft lockup was observed.
Increase the watchdog threshold.

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

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

@@ -247,6 +247,7 @@ install_grub() {
                 case "${SUBARCH}" in
                     "icicle")
                         echo "Installing GRUB for ${SUBARCH} board"
+                        cp ${my_d}/riscv64/grub/90_watchdog-thresh.cfg mountpoint/etc/default/grub.d/
                         # flash-kernel is needed to install the dtb for update-grub: it uses the
                         # /proc/device-tree/model value to pick the correct dtb and as we are in a chroot,
                         # the model value is wrong and we need to use /etc/flash-kernel/machine instead.
@@ -367,6 +368,7 @@ EOF
                         setup_cinocloud mountpoint
                         ;;
                     *)
+                        cp ${my_d}/riscv64/grub/90_watchdog-thresh.cfg mountpoint/etc/default/grub.d/
                         chroot mountpoint apt-get install -qqy u-boot-menu #grub-efi-riscv64
                         efi_target=riscv64-efi
                         chroot mountpoint u-boot-update

live-build/ubuntu-cpc/hooks.d/base/riscv64/grub/90_watchdog-thresh.cfg

@@ -0,0 +1,3 @@
+# When booting with Radeon GPUs a soft lockup was observed. Increase the
+# watchdog threshhold.
+GRUB_CMDLINE_LINUX_DEFAULT="$GRUB_CMDLINE_LINUX_DEFAULT sysctl.kernel.watchdog_thresh=60"