Replace MBEDTLS_MD_CAN_SHA256 with PSA_WANT_ALG_SHA_256

Signed-off-by: Elena Uziunaite <elena.uziunaite@arm.com>
diff --git a/programs/ssl/ssl_test_lib.c b/programs/ssl/ssl_test_lib.c
index 17d36b7..2419bba 100644
--- a/programs/ssl/ssl_test_lib.c
+++ b/programs/ssl/ssl_test_lib.c
@@ -113,7 +113,7 @@
                                     (const unsigned char *) pers,
                                     strlen(pers));
 #elif defined(MBEDTLS_HMAC_DRBG_C)
-#if defined(MBEDTLS_MD_CAN_SHA256)
+#if defined(PSA_WANT_ALG_SHA_256)
     const mbedtls_md_type_t md_type = MBEDTLS_MD_SHA256;
 #elif defined(MBEDTLS_MD_CAN_SHA512)
     const mbedtls_md_type_t md_type = MBEDTLS_MD_SHA512;