HAL_Linux: fixed termios settings on BBB initial boot

this should fix the problem of losing the GPS in flight

libraries/AP_HAL_Linux/UARTDriver.cpp

@@ -150,9 +150,10 @@ void LinuxUARTDriver::begin(uint32_t b, uint16_t rxS, uint16_t txS)
         tcgetattr(_rd_fd, &t);
         cfsetspeed(&t, b);
         // disable LF -> CR/LF
-        t.c_iflag &= ~(BRKINT | ICRNL | IMAXBEL);
+        t.c_iflag &= ~(BRKINT | ICRNL | IMAXBEL | IXON | IXOFF);
         t.c_oflag &= ~(OPOST | ONLCR);
         t.c_lflag &= ~(ISIG | ICANON | IEXTEN | ECHO | ECHOE | ECHOK | ECHOCTL | ECHOKE);
+        t.c_cc[VMIN] = 0;
         tcsetattr(_rd_fd, TCSANOW, &t);
     }