Add description for some cpuid bits

[Dmitry Luhtionov]

--- /usr/src/sys/amd64//amd64/identcpu.c.orig    2013-11-01
14:43:15.000000000 +0200
+++ /usr/src/sys/amd64//amd64/identcpu.c    2013-11-04 12:06:06.000000000
+0200
@@ -366,14 +366,14 @@
                 "\017<b14>"
                 "\020LWP"    /* Lightweight Profiling */
                 "\021FMA4"    /* 4-operand FMA instructions */
-                "\022<b17>"
+                "\022TCE"    /* Translation Cache Extension */
                 "\023<b18>"
                 "\024NodeId"    /* NodeId MSR support */
                 "\025<b20>"
                 "\026TBM"    /* Trailing Bit Manipulation */
                 "\027Topology"    /* Topology Extensions */
-                "\030<b23>"
-                "\031<b24>"
+                "\030PCXC"    /* Core performance counter extensions */
+                "\031PNXC"    /* NB performance counter extensions */
                 "\032<b25>"
                 "\033<b26>"
                 "\034<b27>"