The description of the XUSB_PADCTL_USB3_PAD_MUX_0 register in the Tegra124
documentation implies that all functions (pcie, usb3 and sata) can be
muxed onto to all lanes (pcie lanes 0-4 and sata lane 0). However, it has
been confirmed that this is not the case and the mux'ing options much more
limited. Unfortunately, the public documentation has not been updated to
reflect this and so detail the actual mux'ing options here by function: