Replace MBEDTLS_ERR_OID_BUF_TOO_SMALL with PSA_ERROR_BUFFER_TOO_SMALL

Remove the definition of `MBEDTLS_ERR_OID_BUF_TOO_SMALL` in `x509_oid.h`,
and use the corresponding PSA error instead.

```
git grep -l MBEDTLS_ERR_OID_BUF_TOO_SMALL | xargs perl -i -pe 's/\bMBEDTLS_ERR_OID_BUF_TOO_SMALL\b/PSA_ERROR_BUFFER_TOO_SMALL/p'
edit library/x509_oid.h
```

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/include/mbedtls/x509.h b/include/mbedtls/x509.h
index 9d988a1..5a3bd8a 100644
--- a/include/mbedtls/x509.h
+++ b/include/mbedtls/x509.h
@@ -498,7 +498,7 @@
  * \param oid       OID to translate
  *
  * \return          Length of the string written (excluding final NULL) or
- *                  MBEDTLS_ERR_OID_BUF_TOO_SMALL in case of error
+ *                  PSA_ERROR_BUFFER_TOO_SMALL in case of error
  */
 int mbedtls_oid_get_numeric_string(char *buf, size_t size, const mbedtls_asn1_buf *oid);