cpufreq: dt-platdev: Support building as module

Make the cpufreq platdev driver as tristate so that it can be built
as loadable module.

Also add MODULE_LICENSE to support building as module.

Signed-off-by: Zhipeng Wang <zhipeng.wang_1@nxp.com>
[ Viresh: Merged two commits, included module.h ]
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

Author: zhipeng66

drivers/cpufreq/Kconfig

@@ -218,7 +218,7 @@ config CPUFREQ_DT
 	  If in doubt, say N.
 
 config CPUFREQ_DT_PLATDEV
-	bool
+	tristate "Generic DT based cpufreq platdev driver"
 	help
 	  This adds a generic DT based cpufreq platdev driver for frequency
 	  management.  This creates a 'cpufreq-dt' platform device, on the

drivers/cpufreq/cpufreq-dt-platdev.c

@@ -5,6 +5,7 @@
  */
 
 #include <linux/err.h>
+#include <linux/module.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
 
@@ -217,3 +218,4 @@ static int __init cpufreq_dt_platdev_init(void)
 			       sizeof(struct cpufreq_dt_platform_data)));
 }
 core_initcall(cpufreq_dt_platdev_init);
+MODULE_LICENSE("GPL");