installkernel-bls: remove unnecessary check for GRUB_ENABLE_BLSCFG=true
    
    A BLS configuration is the default and in this case the installkernel-bls
    script is used. For a non-BLS configuration the grubby-deprecated package
    installs an installkernel that uses the new-kernel-pkg script.
    
    So there is no need to check for GRUB_ENABLE_BLSCFG=true. Also, this check
    is wrong for s390x and was causing the installkernel-bls script to no call
    kernel-install on this platform.
    
    Resolves: rhbz#1647721
    
    Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>