pinctrl: exynos5440: fix issues reported by prevent tool

This patch fixes issues reported by prevent tool.

Signed-off-by: Thomas Abraham <thomas.ab@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>
[Drop hunk already in-tree from a patch by Wei Yongjun]
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>