libxc: remove obsolete comment.

Seems to predate Xen 3.0...

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
xen-unstable changeset:   23707:9afeab10a65d
xen-unstable date:        Sat Jul 16 09:18:45 2011 +0100

tools/libxc/xenctrl.h

@@ -1108,10 +1108,6 @@ int xc_lockprof_query(xc_interface *xch,
  * should be unmapped with munmap and should follow the same rules as mmap
  * regarding page alignment.  Returns NULL on failure.
  *
- * In Linux, the ring queue for the control channel is accessible by mapping
- * the shared_info_frame (from xc_domain_getinfo()) + 2048.  The structure
- * stored there is of type control_if_t.
- *
  * @parm xch a handle on an open hypervisor interface
  * @parm dom the domain to map memory from
  * @parm size the amount of memory to map (in multiples of page size)