docs(spm): update FF-A manifest binding

- Add security state attribute to memory and device regions.
- Rename device region reg attribution to base-address aligned with
  memory regions.
- Add pages-count field to device regions.
- Refresh interrupt attributes description in device regions.

Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
Change-Id: I901f48d410edb8b10f65bb35398b80f18105e427