Fix off by one error calculating the maximum next index in binds_get

[nomis]

For a device with 16 entries in the binding table and 3 entries per request, the start_indexes should be 0, 3, 6, 9, 12, 15.

The last next_idx will be 15, which is less than the total 16.

[mdeweerd]

Thank you for this fix - this seems good to me, merging it.