Changes

ts_51_011.EF_SMSP: Use integer division during encode

Otherwise we might compute float values and fail encoding like this:

> construct.core.FormatFieldError: Error in path (building) -> tp_vp_minutes
> struct '>B' error during building, given value 169.0

Change-Id: I989669434c7ddee9595ee81a0822f9966907a844