library: replace deprecated symbols with temporary _LEGACY ones

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/library/psa_util.c b/library/psa_util.c
index c354f34..70b80d8 100644
--- a/library/psa_util.c
+++ b/library/psa_util.c
@@ -64,7 +64,7 @@
 #endif
 
 #if defined(PSA_WANT_KEY_TYPE_RSA_PUBLIC_KEY) ||    \
-    defined(PSA_WANT_KEY_TYPE_RSA_KEY_PAIR)
+    defined(MBEDTLS_PSA_WANT_KEY_TYPE_RSA_KEY_PAIR_LEGACY)
 const mbedtls_error_pair_t psa_to_pk_rsa_errors[] =
 {
     { PSA_SUCCESS,                     0 },