Tim,
The ISL1763A is connected to the GPMC bus on the SOM. GPMC is the General Purpose Memory Controller. The GPMC controller has a parallel interface which can be configured as 8 or 16-bit according to the DM3730 technical reference manual.
http://www.ti.com/lit/pdf/sprugn4 The GPMC bus can be used for communicating with NAND, NOR, and a variety of other devices using a parallel type interface. The Ethernet controller on the Torpedo development kit is another device on the same bus. The devices all share a same bus, but each device has different chip select pins.
If you've registered a SOM and/or a kit, you should have access to the downloadable schematics for both the Torpedo SOM and the development kit for the Torpedo SOM.
I confirmed with the hardware designer that the ULPI interface wasn't exposed on the Torpedo SOM which is why we used the GPMC interface to the ISP1763.
adam