ARM: exynos_defconfig: Remove MAX77802 RTC Kconfig symbol

The driver has been removed so the Kconfig symbol is not valid anymore.

Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Reviewed-by: Andi Shyti <andi.shyti@samsung.com>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>