libxc: Enable cpuid performance counter leaf for HVM

In HVM domains the usable performance counters can be checked
automatically only, if cpuid leaf 0x0000000a is accessible.

Signed-off-by: Juergen Gross <juergen.gross@ts.fujitsu.com>
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>

tools/libxc/xc_cpuid_x86.c

@@ -392,6 +392,7 @@ static void xc_cpuid_hvm_policy(
 
     case 0x00000002: /* Intel cache info (dumped by AMD policy) */
     case 0x00000004: /* Intel cache info (dumped by AMD policy) */
+    case 0x0000000a: /* Architectural Performance Monitor Features */
     case 0x80000002: /* Processor name string */
     case 0x80000003: /* ... continued         */
     case 0x80000004: /* ... continued         */