-moved rc.mavlink to the boards optional rc additions (now it's called rc.board_mavlink) to handle board specific mavlink needs (mavlink over usb, ethernet, additional streams, etc.)
-mavlink module will be responsible to usb defaults, therefore less args are needed to be passed to mavlink module if one wants to use mavlink over usb.
-the way to check if connection is usb is by it's designated variable and not by config mode.
* The build is built with SPI4. At run time the signal GPIO_8266_GPIO2 it tested. If it is low the SPI4 is configured. If it is high SPI4 is not configured.
* board_common: Add Notion of Board has bus manifest
* We have RAM problems and can't afford 4 mavlink instances. This only adds logic the rc.board for the fmu-v4 that only has an effect for SYS_AUTOSTART = 4250 (TealOne airframe).
* added a parameter for enabled the smart battery
* start tel1 and tel2 at 921600 and max rate
* turned up the max tx rate on mavlink streams for telem1 and telem2
* turned off mavlink stream for tel1 in 4250_teal. This is connected to TX1 FTDI UART and has issues.
* moved check to 4250 board ID to start mpu9250s for Teal airframe into fmuv4 rc.board.