Update and Add features to Bosch Guardian Board

[Moses Christopher]

The following patches ensure that the Bosch Guardian Board is updated with
the latest feature additions and improvements made in the recent past

On High Level, the following are achieved:
  * Proper handling of USB-ETH Boot in SPL stage
  * Provide Boot stage feedback
  * Store Bootcount in RTC Scratch Registers
  * Save ENV in NAND
  * Handle Linux Boot