PM / devfreq: exynos: Enable building exynos PPMU as module

Export symbols from the PPMU driver needed to build the exynos bus
driver as a module.

Cc: MyungJoo Ham <myungjoo.ham@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Kukjin Kim <kgene.kim@samsung.com>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Punit Agrawal <punit.agrawal@arm.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>

drivers/devfreq/Kconfig

@@ -78,7 +78,7 @@ config ARM_EXYNOS4_BUS_DEVFREQ
 	  This does not yet operate with optimal voltages.
 
 config ARM_EXYNOS5_BUS_DEVFREQ
-	bool "ARM Exynos5250 Bus DEVFREQ Driver"
+	tristate "ARM Exynos5250 Bus DEVFREQ Driver"
 	depends on SOC_EXYNOS5250
 	select DEVFREQ_GOV_SIMPLE_ONDEMAND
 	select PM_OPP

drivers/devfreq/exynos/exynos_ppmu.c

@@ -73,6 +73,7 @@ void busfreq_mon_reset(struct busfreq_ppmu_data *ppmu_data)
 		exynos_ppmu_start(ppmu_base);
 	}
 }
+EXPORT_SYMBOL(busfreq_mon_reset);
 
 void exynos_read_ppmu(struct busfreq_ppmu_data *ppmu_data)
 {
@@ -97,6 +98,7 @@ void exynos_read_ppmu(struct busfreq_ppmu_data *ppmu_data)
 
 	busfreq_mon_reset(ppmu_data);
 }
+EXPORT_SYMBOL(exynos_read_ppmu);
 
 int exynos_get_busier_ppmu(struct busfreq_ppmu_data *ppmu_data)
 {
@@ -114,3 +116,4 @@ int exynos_get_busier_ppmu(struct busfreq_ppmu_data *ppmu_data)
 
 	return busy;
 }
+EXPORT_SYMBOL(exynos_get_busier_ppmu);