PM / devfreq: make event/exynos-nocp DEVFREQ_EVENT_EXYNOS_NOCP tristate

The Kconfig currently controlling compilation of this code is:

event/Kconfig:config DEVFREQ_EVENT_EXYNOS_NOCP
event/Kconfig:  bool "EXYNOS NoC (Network On Chip) Probe DEVFREQ event Driver"

...meaning that it currently is not being built as a module by anyone.

Rather than rip out the existing modular code, Chanwoo indicated
that he'd rather see the driver offered as tristate.

I don't have the hardware for runtime validation, so this change
is only validated for compile and modpost.
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Acked-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>

drivers/devfreq/event/Kconfig

@@ -14,7 +14,7 @@ menuconfig PM_DEVFREQ_EVENT
 if PM_DEVFREQ_EVENT
 
 config DEVFREQ_EVENT_EXYNOS_NOCP
-	bool "EXYNOS NoC (Network On Chip) Probe DEVFREQ event Driver"
+	tristate "EXYNOS NoC (Network On Chip) Probe DEVFREQ event Driver"
 	depends on ARCH_EXYNOS
 	select PM_OPP
 	help