compat.h: drop COMPAT_HANDLE_PARAM()

The need for 8844ed299a ("x86/dmop: Fix compat_dm_op() ABI") has made
clear that its presence is actively dangerous. At the hypercall entry
points XEN_GUEST_HANDLE_PARAM() should be used anyway (regardless of
whether these are native or compat entry points), and passing around
handles internally shouldn't use their compat representation either.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/include/xen/compat.h
+++ b/xen/include/xen/compat.h
@@ -25,9 +25,6 @@
     __DEFINE_COMPAT_HANDLE(name, name)
 #define COMPAT_HANDLE(name)          __compat_handle_ ## name
 
-/* NB: it is assumed that if an arch uses the compat layer it does not
- * distinguish handles from parameter handles. */
-#define COMPAT_HANDLE_PARAM(name)    __compat_handle_ ## name
 /* Is the compat handle a NULL reference? */
 #define compat_handle_is_null(hnd)        ((hnd).c == 0)