ARM: SAMSUNG: Fix on drive strength value

This patch fixes on defined drive strength value for GPIO.
According to data sheet, if we want drive strength 1x, the value
should be 00(b), if 2x should be 10(b), if 3x should be 01(b),
and if 4x should be 11(b). Also fixes comment(from S5C to S5P).

Reported-by: Janghyuck Kim <janghyuck.kim@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>