PSA service config build: note why we aren't disabling cipher and md

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/tests/scripts/all.sh b/tests/scripts/all.sh
index 9bd2c2d..6e5d923 100755
--- a/tests/scripts/all.sh
+++ b/tests/scripts/all.sh
@@ -1567,6 +1567,8 @@
   scripts/config.py unset MBEDTLS_VERSION_FEATURES
   # Crypto stuff with no PSA interface
   scripts/config.py unset MBEDTLS_BASE64_C
+  # Keep MBEDTLS_CIPHER_C because psa_crypto_cipher, CCM and GCM need it.
+  # Keep MBEDTLS_MD_C because deterministic ECDSA needs it for HMAC_DRBG.
   scripts/config.py unset MBEDTLS_NIST_KW_C
   scripts/config.py unset MBEDTLS_PEM_PARSE_C
   scripts/config.py unset MBEDTLS_PEM_WRITE_C