boot: Add boot status record to shared data area

Implement the functions declared in boot_record.h and add
each BOOT_RECORD TLV's CBOR encoded binary data (one TLV entry per
image) to a shared data area between the bootloader and the runtime SW.
These data units are stored in a TLV format (in the shared area too) and
contain certain attributes of the given image / SW component such as:
- SW type (role of the software component)
- SW version
- Signer ID (identifies the signing authority)
- Measurement value (hash of the image)
- Measurement type (algorithm used to calculate the measurement value)

Preserving all these image attributes from the boot stage for use by
later runtime services is known as a measured boot. The list of the
shared attributes is based on the recommendations of Arm's Platform
Security Architecture (PSA).
The main purpose of this patch is to create the prerequisites of an
attestation service by providing these measurements.

The boot_record.c and boot_status.h (originally tfm_boot_status.h) files
were copied (with modifications) from the Trusted Firmware-M project
(https://www.trustedfirmware.org/about/

).
Hash of the source commit: 08d5572b4bcee306d8cf709c2200359a22d5b72c.

Change-Id: I37a8e7b10d5bf80a581651ffaf65b3cba45eaff2
Signed-off-by: David Vincze <david.vincze@arm.com>