bs-upload-kernel: Drop BS_SUFFIX (JSC-SLE#5501, boo#1211226, bsc#1218184)
    
    BS_SUFFIX was used by SLE12 SP1 for Arm. This release is no longer
    maintained, and this feature gets no testing.
    
    Substantial changes to this script are required, and it's unlikely this
    feture would keep working after that.