3D SIV switch block bug

[vaughnbetz]

The custom switch block in this architecture has a bug:

        <switchfuncs>
            **<!-- Straight -->**   # Delete this comment (out of date)
            <func type="la" formula="t"/>
            <!-- left to above -->
            <func type="lu" formula="t"/>
            <!-- top to under -->
            <func type="ra" formula="t"/>
            <!-- right to above -->
            <func type="ru" formula="t"/>
            <!-- right to under -->
            <func type="ta" formula="t"/>
            <!-- top to above -->
            <func type="tu" formula="t"/>
            <!-- top to under -->
            <func type="ba" formula="t"/>
            <!-- bottom to above -->
            <func type=**"lu"** formula="t"/>   # should be "bu"

Context

This led to RR switches from die 1 -> die 0 (down) than from die 0 to die 1.