xen/xsm: flask: Fix compilation when CONFIG_COMPAT=n

The commit f7d29f7b "flask: add compat mode guest support" introduces
build breakage on ARM when XSM is enabled. It's because ARM doesn't use
compat mode.

flask_op.c:794:34: fatal error: compat/event_channel.h: No such file or directory
 #include <compat/event_channel.h>

Signed-off-by: Julien Grall <julien.grall@linaro.org>
Acked-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Acked-by: Ian Campbell <ian.campbell@citrix.com>

xen/xsm/flask/flask_op.c

@@ -785,7 +785,7 @@ ret_t do_flask_op(XEN_GUEST_HANDLE_PARAM(xsm_op_t) u_flask_op)
     return rv;
 }
 
-#ifndef COMPAT
+#if defined(CONFIG_COMPAT) && !defined(COMPAT)
 #undef _copy_to_guest
 #define _copy_to_guest copy_to_compat
 #undef _copy_from_guest