[FDT] Support modifying of bootargs even if no bootargs node exists.
Upgraded to bitthunder that support "powershell"
[COMMAND] Added an fdt command for modifying FDTs.
[MACH] Zynq - Added a weak symbol for ps7_post_config in case it doesn't exist.
[COMMON] Added fdt_support routines.
[BT] Upgraded to latest BT to support new boot features.