Measured Boot: add function for hash calculation

This patch adds 'calc_hash' function using Mbed TLS library
required for Measured Boot support.

Change-Id: Ifc5aee0162d04db58ec6391e0726a526f29a52bb
Signed-off-by: Alexei Fedorov <Alexei.Fedorov@arm.com>
6 files changed