The old custom matrix code for Preonic rev3 was relying on the
`matrix_col_t` type, because the code actually reads the row pins and
assembles the state for whole columns, and then transposes the matrix in
the custom debouncing code. Restore that type (which is no longer
defined by the core QMK code) to make the custom matrix code work
properly (when `matrix_row_t` was used instead of `matrix_col_t`, the
state of two electrical rows was lost, and those electrical rows
corresponded to the bottom physical row, which did not work).