ARM: SAMSUNG: remove unused SAMSUNG_GPIOLIB_4BIT Kconfig parameter

This removes the SAMSUNG_GPIOLIB_4BIT Kconfig parameter,
which was no longer used anywhere in the source code
and Makefiles.

Signed-off-by: Michael Opdenacker <michael.opdenacker@free-electrons.com>
Reviewed-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>