avdt_ad_open_req() function

* Function avdt_ad_open_req * Description This function is called by a CCB or SCB to open a transport * channel. This function allocates and initializes a * transport channel table entry. The channel can be opened * in two roles: as an initiator or acceptor. When opened * as an initiator the function will start an L2CAP connection. * When opened as an acceptor the function simply configures * the table entry to listen for an incoming channel. * Returns Nothing.