ARM: exynos_defconfig: Enable CONFIG_LOCKUP_DETECTOR

On enabling CONFIG_LOCKUP_DETECTOR the kernel to act as a watchdog
to detect hard and soft lockups. Enabling CONFIG_LOCKUP_DETECTOR
don't introduce much overhead on exyons SOC.
(CONFIG_LOCKUP_DETECTOR is enabled on multi_v7_defconfig.)

Tested on Exynos5422 ODROID XU3 board.

Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Anand Moon <moon.linux@yahoo.com>
Signed-off-by: Kukjin Kim <kgene@kernel.org>