Figure out why htmlgen is reporting unknown bits

Latest run of htmlgen gave the following output;
```
Loading tilegrid.
Writing ./html/artix7/index.html
Writing ./html/artix7/tile_bram_l.html
unused: 533, unknown: 11, known: 2016, total: 2560, percentage: 78.75% (99.57%)
Writing ./html/artix7/tile_bram_r.html
unused: 533, unknown: 11, known: 2016, total: 2560, percentage: 78.75% (99.57%)
Writing ./html/artix7/tile_clbll_l.html
unused: 50, unknown: 8, known: 2246, total: 2304, percentage: 97.48% (99.65%)
Writing ./html/artix7/tile_clbll_r.html
unused: 50, unknown: 8, known: 2246, total: 2304, percentage: 97.48% (99.65%)
Writing ./html/artix7/tile_clblm_l.html
unused: 40, unknown: 0, known: 2264, total: 2304, percentage: 98.26% (100.00%)
Writing ./html/artix7/tile_clblm_r.html
unused: 40, unknown: 0, known: 2264, total: 2304, percentage: 98.26% (100.00%)
Writing ./html/artix7/tile_dsp_l.html
unused: 672, unknown: 106, known: 1782, total: 2560, percentage: 69.61% (95.86%)
Writing ./html/artix7/tile_dsp_r.html
unused: 672, unknown: 106, known: 1782, total: 2560, percentage: 69.61% (95.86%)
Writing ./html/artix7/tile_hclk_l.html
unused: 390, unknown: 4, known: 438, total: 832, percentage: 52.64% (99.52%)
Writing ./html/artix7/tile_hclk_r.html
unused: 390, unknown: 0, known: 442, total: 832, percentage: 53.12% (100.00%)
Writing ./html/artix7/tile_int_l.html
unused: 36, unknown: 30, known: 1598, total: 1664, percentage: 96.03% (98.20%)
Writing ./html/artix7/tile_int_r.html
unused: 36, unknown: 30, known: 1598, total: 1664, percentage: 96.03% (98.20%)
```

I'm pretty sure we understand all bits in the `clbl` and `int` tiles, however they are being reported as less than 100%.

This issue is to figure out why this is happening and fix.