01fips: fix HMAC file path resolution
    
    There is a small regression in #343: when handling the 'separate boot
    partition' case, we're checking for the kernel image in the wrong
    location: `BOOT_IMAGE` is the `/boot`-relative path to the kernel image,
    so `/boot/${BOOT_IMAGE_PATH}/${BOOT_IMAGE}` expands to e.g.
    `/boot/mysubdir1/mysubdir2/mysubdir1/mysubdir2/vmlinuz...`.
    
    We should be using `BOOT_IMAGE_NAME` here instead (and in fact, the next
    if-statement does this correctly, so it might've just been accidentally
    left out of #343).
    
    patch_name: 0053.patch
    present_in_specfile: true
    location_in_specfile: 53
    squash_commits: true