Convert to new override syntax

This is the result of automated script conversion:

scripts/contrib/convert-overrides.py <oe-core directory>

converting the metadata to use ":" as the override character instead of "_".

(From OE-Core rev: 42344347be29f0997cc2f7636d9603b1fe1875ae)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/systemd-boot.bbclass

@@ -28,7 +28,7 @@ efi_populate() {
         done
 }
 
-efi_iso_populate_append() {
+efi_iso_populate:append() {
         cp -r $iso_dir/loader ${EFIIMGDIR}
 }