systemd-boot.bbclass: Add configuration data to secondary EFI partition

The secondary EFI partition is used when booting in EFI mode, and
without the configuration data we don't get any boot targets.

Partial fix to [YOCTO #11503].

(From OE-Core master rev: 84aa7a00810e135fdad3f77bdb1da7d1f5fb8627)

(From OE-Core rev: 915b01258ef426392bb9052c345f952670db4450)

Signed-off-by: California Sullivan <california.l.sullivan@intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/systemd-boot.bbclass

@@ -50,6 +50,7 @@ efi_iso_populate() {
         efi_populate $iso_dir
         mkdir -p ${EFIIMGDIR}/${EFIDIR}
         cp $iso_dir/${EFIDIR}/* ${EFIIMGDIR}${EFIDIR}
+        cp -r $iso_dir/loader ${EFIIMGDIR}
         cp $iso_dir/vmlinuz ${EFIIMGDIR}
         EFIPATH=$(echo "${EFIDIR}" | sed 's/\//\\/g')
         echo "fs0:${EFIPATH}\\${DEST_EFI_IMAGE}" > ${EFIIMGDIR}/startup.nsh