x86/pv-shim: fix grant table operations for 32-bit guests

When switching to call the shim functions from the normal handlers, the
compat_grant_table_op() function was omitted, leaving it calling the
real grant table operations in !PV_SHIM_EXCLUSIVE builds. This leaves a
32-bit shim guest failing to set up its real grant table with the parent
hypervisor.

Fixes: e7db635f44 ("x86/pv-shim: Don't modify the hypercall table")
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>

xen/common/compat/grant_table.c

@@ -63,6 +63,11 @@ int compat_grant_table_op(
     unsigned int i, cmd_op;
     XEN_GUEST_HANDLE_PARAM(void) cnt_uop;
 
+#ifdef CONFIG_PV_SHIM
+    if ( unlikely(pv_shim) )
+        return pv_shim_grant_table_op(cmd, uop, count);
+#endif
+
     set_xen_guest_handle(cnt_uop, NULL);
     cmd_op = cmd & GNTTABOP_CMD_MASK;
     if ( cmd_op != GNTTABOP_cache_flush )