01fips: add / in BOOT_IMAGE_HMAC filename for clarity
    
    It's already the case the `BOOT_IMAGE_PATH` today, in the non-empty
    case, includes a trailing `/`, but let's add it to the path we build
    here too to make it more obvious.
    
    patch_name: 0055.patch
    present_in_specfile: true
    location_in_specfile: 55
    squash_commits: true