HAL_Linux: Add FRAM HAL driver support for non-volatile storage

Support for File System starage mode is retained, appropriate Storage mode can be set by defining USE_FS_STORAGE for File System storage aand US_FRAM_STORAGE for FRAM storage.
Note: FS storage and FRAM storage are never synced as of now.
AP_HAL: Add EEPROM instance to HAL to support non-volatile storage HAL drivers
HAL_Empty: add EmptyEEPROM instance to HAL_Empty

Note: only HAL_Linux has EEPROM support, EmptyEEPROM needs to be used for other HALs, this change is pending as of now.