Docs: Structure the Design documents

- gather documents in folders:
   "booting" for secure boot related designs
   "services" for Secure services and SPM
   "software" for general TF-M framework design and rules
- add short document names in indexes

Signed-off-by: Anton Komlev <anton.komlev@arm.com>
Change-Id: I4efd309c186e431cf24c3259a35bfef53e2eb24c
diff --git a/docs/configuration/profiles/tfm_profile_medium.rst b/docs/configuration/profiles/tfm_profile_medium.rst
index cd3bb34..3141221 100644
--- a/docs/configuration/profiles/tfm_profile_medium.rst
+++ b/docs/configuration/profiles/tfm_profile_medium.rst
@@ -467,7 +467,7 @@
 
 .. [RFC7251] `AES-CCM Elliptic Curve Cryptography (ECC) Cipher Suites for TLS <https://tools.ietf.org/html/rfc7251>`_
 
-.. [CRYPTO-DESIGN] :doc:`Crypto design </design_docs/tfm_crypto_design>`
+.. [CRYPTO-DESIGN] :doc:`Crypto design </design_docs/services/tfm_crypto_design>`
 
 .. [ITS-INTEGRATE] :doc:`ITS integration guide </integration_guide/services/tfm_its_integration_guide>`