Hi Biser,
USB1 has no mux mode to do this is pinmux.
But in the note it written as "(13) The internal USB PHY can be configured to multiplex the UART3_TX or UART3_RX signals to this terminal. For more details refer to USB GPIO Details section of the AM335x Technical
Reference Manual."
Kindly let me know how it can be done in code.
Rgds,
chandra