SPM: Remove memory data list from template

- Move stack member out of memory data, and put it into partition
  static type.
- Move the isolation level 3 data 'mems' into static info. There is
  only one member included in it at present, but eventually, this
  member would include multiple memory items.

Change-Id: I007fa622b3e65887fa556fda253d7a6672c08cbf
Signed-off-by: Ken Liu <Ken.Liu@arm.com>