Replace `MBEDTLS_MD_CAN_SHA512` with `PSA_WANT_ALG_SHA_512`

Signed-off-by: Gabor Mezei <gabor.mezei@arm.com>
diff --git a/programs/ssl/ssl_test_common_source.c b/programs/ssl/ssl_test_common_source.c
index 079b14d..ff3b97e 100644
--- a/programs/ssl/ssl_test_common_source.c
+++ b/programs/ssl/ssl_test_common_source.c
@@ -292,7 +292,7 @@
 #endif
 
 uint16_t ssl_sig_algs_for_test[] = {
-#if defined(MBEDTLS_MD_CAN_SHA512)
+#if defined(PSA_WANT_ALG_SHA_512)
     MBEDTLS_SSL_SIG_ALG(MBEDTLS_SSL_HASH_SHA512)
 #endif
 #if defined(PSA_WANT_ALG_SHA_384)