cpufreq: Select PM_OPP rather than depending on it

PM_OPP is a helper library used by several of the existing cpufreq drivers.
Some of the drivers select this symbol while others depend on it and rely
on the architecture to enable it. Make this behaviour more consistent and
obvious by having all the drivers select the symbol. This will also allow
better build coverage of the affected drivers.

Signed-off-by: Mark Brown <broonie@linaro.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
diff --git a/drivers/cpufreq/Kconfig b/drivers/cpufreq/Kconfig
index 38093e2..386dbc9 100644
--- a/drivers/cpufreq/Kconfig
+++ b/drivers/cpufreq/Kconfig
@@ -181,7 +181,8 @@
 
 config GENERIC_CPUFREQ_CPU0
 	tristate "Generic CPU0 cpufreq driver"
-	depends on HAVE_CLK && REGULATOR && PM_OPP && OF
+	depends on HAVE_CLK && REGULATOR && OF
+	select PM_OPP
 	help
 	  This adds a generic cpufreq driver for CPU0 frequency management.
 	  It supports both uniprocessor (UP) and symmetric multiprocessor (SMP)