Respect MBEDTLS_HAVE_TIME in ssl_ticket

Make use of ticket generation time and associated fields
conditional on MBEDTLS_HAVE_TIME, to avoid compile errors
on baremetal.

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/include/mbedtls/ssl_ticket.h b/include/mbedtls/ssl_ticket.h
index fc86542..b8a8a24 100644
--- a/include/mbedtls/ssl_ticket.h
+++ b/include/mbedtls/ssl_ticket.h
@@ -33,7 +33,10 @@
 
 #include "mbedtls/ssl.h"
 #include "mbedtls/cipher.h"
+
+#if defined(MBEDTLS_HAVE_TIME)
 #include "mbedtls/platform_time.h"
+#endif
 
 #if defined(MBEDTLS_USE_PSA_CRYPTO)
 #include "psa/crypto.h"
@@ -57,7 +60,9 @@
 {
     unsigned char MBEDTLS_PRIVATE(name)[MBEDTLS_SSL_TICKET_KEY_NAME_BYTES];
                                                      /*!< random key identifier              */
+#if defined(MBEDTLS_HAVE_TIME)
     mbedtls_time_t MBEDTLS_PRIVATE(generation_time); /*!< key generation timestamp (seconds) */
+#endif
 #if !defined(MBEDTLS_USE_PSA_CRYPTO)
     mbedtls_cipher_context_t MBEDTLS_PRIVATE(ctx);   /*!< context for auth enc/decryption    */
 #else