* feature: added ability to have radio specific menu items in the bootloader
* added enabling/disabling USB access to the RF module via the bootloader
* enable the internal module on EL18, when RF module USB access is enabled
* moved USB switch pin initialization to the NV14/EL18 specific code
* moved EL18 USB switch defines to boot_menu
* feat: added a symbol for RF USB switch menu option on EL18 bootloader