runqemu-internal: cleanup unsed code

runqemu-internal: cleanup unsed code

* remove akita and spitz related code
  They are not supported by runqemu anymore:
  $ runqemu spitz
  Error: unable to classify arg [spitz]
  So remove related code.

* Remove checking of 256M for qemuarm, qemu can check it, for example:
  $ runqemu qemuarm qemuparams="-m 1024"
  [snip]
  qemu: Too much memory for this machine: 1024 MB, maximum 256 MB
  [snip]

Signed-off-by: Robert Yang <liezhi.yang@windriver.com>