This commit does the following
- Add power management lock to CAN driver so that APB frequency does not change
whilst CAN driver is in use
- Fix incorrect flag in can_transmit()
- Refactor can_driver_install() and can_driver_uninstall() so that critical sections
are shorter
- Fix CAN gpio configuration bug on RX pin. Closes#2302
- Add docs about multiple ID configuration and fix example links