ARM: S3C2443: Implement GPIO pull-up/down configuration methods

S3C2443 has two-bits pull-up/pull-down configuration fields in GPIO
registers, but values are differ from other SoCs with two-bits
configuration. gpio-cfg-helpers.h already has prototypes for
s3c2443-style pull-up/down methods, so implement them.

Signed-off-by: Yauhen Kharuzhy <yauhen.kharuzhy@promwad.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>