Fix output for Raspberry Pi 3 if mounpoint is missing

It was accidentally copy-pasted from BeagleBoard

Changelog: None

Signed-off-by: Denis Mosolov <denismosolov@gmail.com>

convert-stage-4.sh

@@ -176,7 +176,7 @@ install_files() {
       ;;
     "raspberrypi3")
       [ ! -d "$primary_dir/uboot" ] && \
-          { log "\t'/boot/efi' mountpoint missing. Adding"; \
+          { log "\t'/uboot' mountpoint missing. Adding"; \
             sudo install -d -m 755 ${primary_dir}/uboot; }
       ;;
   esac