samsung-xcover4lte: use sm-sparse-image-tool

The new option deviceinfo_flash_sparse_samsung_format seems to work fine on the xcover4lte.

Setting deviceinfo_flash_sparse_samsung_format to 1 (and deviceinfo_flash_sparse="true") causes heimdall to no longer hang while the rootfs is being flashed. As there is no official TWRP port for the xcover4lte, flashing via heimdall might be the preferable option.