BL2: Enable ECDSA signature verification

Add the option to use ECDSA signature verification
with PSA Crypto for MCUboot by setting the
MCUBOOT_SIGNATURE_TYPE to EC-P256 / EC-P384 and enabling
MCUBOOT_USE_PSA_CRYPTO in the CMake configuration.
Updating the MCUBOOT_VERSION to have:

- ECDSA signature verification using the PSA Crypto API,
- ECDSA-P384 support.

Signed-off-by: Roland Mikhel <roland.mikhel@arm.com>
Change-Id: Ida24010ca043081743712c75c3a8fe616f61c127
diff --git a/docs/design_docs/booting/tfm_secure_boot.rst b/docs/design_docs/booting/tfm_secure_boot.rst
index 2f92668..be1928a 100644
--- a/docs/design_docs/booting/tfm_secure_boot.rst
+++ b/docs/design_docs/booting/tfm_secure_boot.rst
@@ -368,6 +368,8 @@
 - MCUBOOT_SIGNATURE_TYPE (default: RSA-3072):
     - **RSA-2048:** Image is signed with RSA algorithm and signed with 2048 bit key.
     - **RSA-3072:** Image is signed with RSA algorithm and signed with 3072 bit key.
+    - **EC-P256:** Image is signed with ECDSA P-256 algorithm.
+    - **EC-P384:** Image is signed with ECDSA P-384 algorithm.
 - MCUBOOT_IMAGE_NUMBER (default: 2):
     - **1:** Single image boot, secure and non-secure images are signed and
       updated together.