x86: Don't export interrupt handlers with x86_64

We don't have a way of adjusting these at present so it is best to refuse to
export these functions. This can be implemented later if the API is required.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

include/_exports.h

@@ -13,7 +13,7 @@
 	EXPORT_FUNC(putc, void, putc, const char)
 	EXPORT_FUNC(puts, void, puts, const char *)
 	EXPORT_FUNC(printf, int, printf, const char*, ...)
-#if defined(CONFIG_X86) || defined(CONFIG_PPC)
+#if (defined(CONFIG_X86) && !defined(CONFIG_X86_64)) || defined(CONFIG_PPC)
 	EXPORT_FUNC(irq_install_handler, void, install_hdlr,
 		    int, interrupt_handler_t, void*)