cpu: Fix leftovers from the P state cpu frequency calculation

The commit 15b8bfb ("Ignore non-P-state-enabled CPUs when calculating
frequency") and 29f42b5 ("fixed issues with p-state reported CPU
frequencies") fixed frequency calculation for cpu packages but missed
it for cpu cores.  Add it.

This fixes wrong frequency report on my quad-core box: 2072.5% -> 100.0%

Cc: Ivan Shapovalov <intelfx100@gmail.com>
Signed-off-by: Namhyung Kim <namhyung@gmail.com>
diff --git a/src/cpu/cpu_core.cpp b/src/cpu/cpu_core.cpp
index b0dd4da..2caa58d 100644
--- a/src/cpu/cpu_core.cpp
+++ b/src/cpu/cpu_core.cpp
@@ -131,10 +131,9 @@
 	bool is_idle = true;
 	unsigned int i;
 
-
 	/* calculate the maximum frequency of all children */
 	for (i = 0; i < children.size(); i++)
-		if (children[i]) {
+		if (children[i] && children[i]->has_pstates()) {
 			uint64_t f = 0;
 			if (!children[i]->idle) {
 				f = children[i]->current_frequency;
diff --git a/src/cpu/intel_cpus.cpp b/src/cpu/intel_cpus.cpp
index f7b86bc..19ad85c 100644
--- a/src/cpu/intel_cpus.cpp
+++ b/src/cpu/intel_cpus.cpp
@@ -240,7 +240,7 @@
 
 	/* calculate the maximum frequency of all children */
 	for (i = 0; i < children.size(); i++)
-		if (children[i]) {
+		if (children[i] && children[i]->has_pstates()) {
 			uint64_t f = 0;
 			if (!children[i]->idle) {
 				f = children[i]->current_frequency;