Add information about BSP version

[RikardO-HM]

Add how it is possible to read out the information in the mx4 and for the newer platforms.

Example doc for hmx:
To check the information about what release you current have on hmx you can use this command cat /etc/platform-version this is related to the mobility-poky-platform repo git hash.

[RikardO-HM]

also add where the user can find partnumber and serial number (/proc/device-tree/choosen/”product” )