Reduce code size when mbedtls_x509_*_info() unused

Introduce MBEDTLS_X509_INFO to indicate the availability of the
mbedtls_x509_*_info() function and closely related APIs. When this is
not defined, also omit name and description from
mbedtls_oid_descriptor_t, and omit OID arrays, macros, and types that
are entirely unused. This saves several KB of code space.

Signed-off-by: Hanno Becker <hanno.becker@arm.com>
Signed-off-by: Chris Jones <christopher.jones@arm.com>
diff --git a/include/mbedtls/x509_csr.h b/include/mbedtls/x509_csr.h
index b1dfc21..b9e5b93 100644
--- a/include/mbedtls/x509_csr.h
+++ b/include/mbedtls/x509_csr.h
@@ -121,6 +121,7 @@
 int mbedtls_x509_csr_parse_file( mbedtls_x509_csr *csr, const char *path );
 #endif /* MBEDTLS_FS_IO */
 
+#if defined(MBEDTLS_X509_INFO)
 /**
  * \brief          Returns an informational string about the
  *                 CSR.
@@ -135,6 +136,7 @@
  */
 int mbedtls_x509_csr_info( char *buf, size_t size, const char *prefix,
                    const mbedtls_x509_csr *csr );
+#endif
 
 /**
  * \brief          Initialize a CSR