SST: Add PSA Protected Storage header

Adds the PSA Protected Storage API header file to the interface
directory.

Derived from Git SHA a431fb9758b4cc315e0ce0083a56e13a9265f61f in the
following repository https://github.com/arm-software/psa-arch-tests

Change-Id: I0f063dbaef7e2560e0b2f07e38f0bb3d80643783
Signed-off-by: Jamie Fox <jamie.fox@arm.com>
1 file changed