correctly.

The only instances I could find are here.  There are reads of the
MDR register in kernel/gdb-stub.c, but that's harmless.  Although,
frankly, __builtin_return_address(0) might be a better thing in
those cases.  Certainly MDR isn't going to contain anything else
that might be useful...

Signed-off-by: Richard Henderson  <rth@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>