conf: Update homescreen kernel path

   /usr/share/gallery/kernel_blob.bin
   has been relocated to:
   /usr/share/flutter/gallery/flutter_assets/kernel_blob.bin

Relate-to: https://booting.oniroproject.org/rzr/meta-oniro-blueprint-flutter/-/issues/3


Signed-off-by: Philippe Coval <philippe.coval.ext@huawei.com>