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.h b/programs/ssl/ssl_test_lib.h
index 1da2dfb..7eed56c 100644
--- a/programs/ssl/ssl_test_lib.h
+++ b/programs/ssl/ssl_test_lib.h
@@ -21,7 +21,7 @@
 #elif defined(MBEDTLS_ENTROPY_C) && defined(MBEDTLS_CTR_DRBG_C)
 #define HAVE_RNG
 #elif defined(MBEDTLS_ENTROPY_C) && defined(MBEDTLS_HMAC_DRBG_C) &&     \
-    (defined(MBEDTLS_MD_CAN_SHA256) || defined(MBEDTLS_MD_CAN_SHA512))
+    (defined(PSA_WANT_ALG_SHA_256) || defined(MBEDTLS_MD_CAN_SHA512))
 #define HAVE_RNG
 #endif