The only real contraint on the raw buffer is that it is large
enough to contain 2 coordinates. Larger buffers are therefore
allowed and the extra data will simply be ignored.
Note = trying to impose a strict sizing on the raw buffer causes
several failures in test suites. This suggests that it is
quite common to use larger buffer to store raw signatures.
Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>