cpufreq: Select IRQ_WORK if CPU_FREQ_GOV_COMMON is set

Commit 0eb463be3436 (cpufreq: governor: Replace timers with utilization
update callbacks) made CPU_FREQ select IRQ_WORK, but that's not
necessary, as it is sufficient for IRQ_WORK to be selected by
CPU_FREQ_GOV_COMMON, so modify the cpufreq Kconfig to that effect.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

drivers/cpufreq/Kconfig

@@ -3,7 +3,6 @@ menu "CPU Frequency scaling"
 config CPU_FREQ
 	bool "CPU Frequency scaling"
 	select SRCU
-	select IRQ_WORK
 	help
 	  CPU Frequency scaling allows you to change the clock speed of 
 	  CPUs on the fly. This is a nice method to save power, because 
@@ -20,6 +19,7 @@ config CPU_FREQ
 if CPU_FREQ
 
 config CPU_FREQ_GOV_COMMON
+	select IRQ_WORK
 	bool
 
 config CPU_FREQ_BOOST_SW