I doubt will be possible.
Usb Host controller must be on the Soc and for sure TI Soc doesn't have Usb 3.0 host controller.

And to use an external usb host controller chip there should be a pci-e bus and even here I doubt that TI Soc has it.

Maybe it should be possible to use a Usb 3.0 to eMMC bridge chip (if this exists).
A complex thing like "when usb cable is not inserted eMMC is connected to TI Soc, when usb cable is inserted and the user has choosed to share eMMC, the eMMC is detached from TI Soc and attached to Usb 3.0 to eMMC bridge".