Swap initializations of PSA Crypto and Mbed TLS platform

As PSA Crypto is independent of Mbed TLS, `psa_crypto_init()` must
eventually work standalone, and in particular not require a prior
call to `mbedtls_platform_init()`. At the moment, however, it might
still rely on HW drivers being initialized by `mbedtls_platform_init()`,
and so the latter should be invoked before `psa_crypto_init()`. This
commit changes the order of the calls accordingly.

In general, the relation between of `psa_crypto_init()` and
`mbedtls_platform_init()` still needs to be discussed and documented,
and once that's done, the code might need revision. As it stands,
however, it should work with current implementations of
`psa_crypto_init()` and `mbedtls_platform_init()`.

Author: Hanno Becker

tls-client/main.cpp

@@ -55,6 +55,11 @@ int main()
 {
     int exit_code = MBEDTLS_EXIT_FAILURE;
 
+    if((exit_code = mbedtls_platform_setup(NULL)) != 0) {
+        printf("Platform initialization failed with error %d\r\n", exit_code);
+        return MBEDTLS_EXIT_FAILURE;
+    }
+
 #if defined(MBEDTLS_USE_PSA_CRYPTO)
     /*
      * Initialize underlying PSA Crypto implementation.
@@ -73,10 +78,6 @@ int main()
     }
 #endif /* MBEDTLS_USE_PSA_CRYPTO */
 
-    if((exit_code = mbedtls_platform_setup(NULL)) != 0) {
-        printf("Platform initialization failed with error %d\r\n", exit_code);
-        return MBEDTLS_EXIT_FAILURE;
-    }
     /*
      * The default 9600 bps is too slow to print full TLS debug info and could
      * cause the other party to time out.