riscv: correct installation path of dtbs

U-Boot with distroboot has:

efi_dtb_prefixes=/ /dtb/ /dtb/current/

So we should install the device-trees into dtb/ and not dtbs/ on the EFI
system partition.

Fixes: 365435ad2d ("riscv: copy device trees to the ESP")
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>

debian/changelog

@@ -1,3 +1,9 @@
+livecd-rootfs (25.04.11) UNRELEASED; urgency=medium
+
+  * riscv: copy device trees dtb/ in ESP
+
+ -- Heinrich Schuchardt <heinrich.schuchardt@canonical.com>  Mon, 27 Jan 2025 13:42:35 +0100
+
 livecd-rootfs (25.04.10) plucky; urgency=medium
 
   * riscv: copy device trees to the ESP. Fixes (LP: #2095415)

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

@@ -365,7 +365,7 @@ EOF
                     "mountpoint/usr/lib/linux-image-$kver"
                     "mountpoint/lib/firmware/$kver/device-tree"
                 )
-                dtb_tgt_dir="mountpoint/boot/efi/dtbs/"
+                dtb_tgt_dir="mountpoint/boot/efi/dtb/"
                 mkdir -p "$dtb_tgt_dir"
                 for src_dir in "${dtb_src_dirs[@]}"; do
                     [ -d "$src_dir" ] && cp -r -v "$src_dir"/* "$dtb_tgt_dir" || echo "Skipping missing: $src_dir"