x86/mwait-idle: add Knights Mill CPUID

Add Knights Mill (KNM) to the list of CPUIDs supported by mwait-idle.

Signed-off-by: Piotr Luc <piotr.luc@xxxxxxxxx>
Signed-off-by: Len Brown <len.brown@xxxxxxxxx>
[Linux commit: a2c1bc645e87346150516b3abf1933ed29d0f48b]
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/cpu/mwait-idle.c
+++ b/xen/arch/x86/cpu/mwait-idle.c
@@ -946,6 +946,7 @@ static const struct x86_cpu_id intel_idl
 	ICPU(0x9e, skl),
 	ICPU(0x55, skx),
 	ICPU(0x57, knl),
+	ICPU(0x85, knl),
 	ICPU(0x5c, bxt),
 	ICPU(0x5f, dnv),
 	{}