ARM: exynos_defconfig: Disable big.LITTLE switcher

Disable big.LITTLE switcher in order to allow automatic usage of
cpufreq-dt driver on Exynos542x/Exynos5800 SoCs based boards.

This change should not cause any problems as arm_big_little[_dt]
driver (which is using big.LITTLE switcher support to do the "real"
big.LITTLE switching work) is not used on any Exynos SoC based
board currently.

Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Tested-by: Markus Reichl <m.reichl@fivetechno.de>
Reviewed-by: Javier Martinez Canillas <javier@osg.samsung.com>
Tested-by: Javier Martinez Canillas <javier@osg.samsung.com>
Reviewed-by: Anand Moon <linux.amoon@gmail.com>
Tested-by: Anand Moon <linux.amoon@gmail.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>