[tools][lkboot] expand transfer buffer

This is a bit of a hack.
[lib][debugcommands] preflight the address to dump with the mmu (if present)
[list] Add list_length
[pktbuf] Make default behavior to block until a pktbuf is available
[minip] Update packet test
[gem] Make TX path asynchronous
[zynq] Add slcr commands and pull out DDR config