Setting CONFIG_IPK_FILES_CHECKSUMS=y causes sha256 checksum files to be
included with the packages to check for corruption. This commit fixes two
issues:
- /sbin/pkg_check was being removed incorrectly if IPK_FILES_CHECKSUMS=y
- checksums were being saved in the wrong file
Signed-off-by: Xu Wang <xwang1498@gmx.com>