ARM: exynos_defconfig: Enable cpufreq-dt driver

With the latest patches the cpufreq-dt can be used on multiple
Exynos SoCs: 3250, 4210, 4212, 4412 and 5250.

Enable it along with default ondemand governor to conserve the energy,
reduce temperature while maintaining acceptable performance.
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Reviewed-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Kukjin Kim <kgene@kernel.org>

arch/arm/configs/exynos_defconfig

@@ -27,6 +27,8 @@ CONFIG_ARM_APPENDED_DTB=y
 CONFIG_ARM_ATAG_DTB_COMPAT=y
 CONFIG_CMDLINE="root=/dev/ram0 rw ramdisk=8192 initrd=0x41000000,8M console=ttySAC1,115200 init=/linuxrc mem=256M"
 CONFIG_CPU_FREQ=y
+CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND=y
+CONFIG_CPUFREQ_DT=y
 CONFIG_CPU_IDLE=y
 CONFIG_ARM_EXYNOS_CPUIDLE=y
 CONFIG_VFP=y