Fix build of v3.6 with unset MBEDTLS_DHM_C but MBEDTLS_USE_PSA_CRYPTO set (fixes Mbed-TLS#9188)

Avoid compiler warning about size comparison (like in commit 7910cdd):

Clang builds fail, warning about comparing uint8_t to a size that may be >255.

Signed-off-by: Michael Schuster <[email protected]>

Author: misch7

ChangeLog.d/fix-clang-psa-build-without-dhm.txt

@@ -0,0 +1,3 @@
+Bugfix
+   * Fix Clang compilation error when MBEDTLS_USE_PSA_CRYPTO is enabled
+     but MBEDTLS_DHM_C is disabled. Reported by Michael Schuster in #9188.

library/ssl_tls12_server.c

@@ -3921,7 +3921,7 @@ static int ssl_parse_client_key_exchange(mbedtls_ssl_context *ssl)
 #if defined(MBEDTLS_USE_PSA_CRYPTO)
         psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
         psa_status_t destruction_status = PSA_ERROR_CORRUPTION_DETECTED;
-        uint8_t ecpoint_len;
+        size_t ecpoint_len;
 
         mbedtls_ssl_handshake_params *handshake = ssl->handshake;