mbedtls: add support for v3.x

Version 3.4.0 adds a lot of improvements and fixes (a notable one
being initial support for PKCS7 CMS), but since this is a pretty
big jump, let's keep both versions for a while, so the v2.x users
can upgrade to 3.x in a timely manner if needed.

Signed-off-by: Beniamin Sandu <beniaminsandu@gmail.com>
Signed-off-by: Khem Raj <raj.khem@gmail.com>