The dom0_ops implementation wasn't matching the interface definition,

The dom0_ops implementation wasn't matching the interface definition,
leading to ill messages when X starts up (and potentially to other
problems). The attached patch fixes that. However, it also points out
that there is a potential disagreement between the dom0_ops interface
and the internal MTRR interface - the former expects an unsigned
register number from the domain, the latter wants a signed one and does
a lookup when it's negative. I would think that the lookup code should
just be ripped out of xen/arch/x86/mtrr/main.c.

Signed-off-by: Jan Beulich <JBeulich@novell.com>