[CPUFREQ] constify cpufreq_driver where possible.

Not all cases are possible due to ->flags being set at runtime
on some drivers.

Signed-off-by: Dave Jones <davej@redhat.com>
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index 0899e2c..3a25235 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -225,8 +225,8 @@
 #define CPUFREQ_PM_NO_WARN	0x04	/* don't warn on suspend/resume speed
 					 * mismatches */
 
-int cpufreq_register_driver(struct cpufreq_driver *driver_data);
-int cpufreq_unregister_driver(struct cpufreq_driver *driver_data);
+int cpufreq_register_driver(const struct cpufreq_driver *driver_data);
+int cpufreq_unregister_driver(const struct cpufreq_driver *driver_data);
 
 
 void cpufreq_notify_transition(struct cpufreq_freqs *freqs, unsigned int state);