ARM: EXYNOS: Remove unused code in common.h

PINCTRL_EXYNOS is always selected by Exynos platform in its
machine Kconfig. Thus the code in the else part is never used.
Remove it.

Signed-off-by: Sachin Kamat <sachin.kamat@samsung.com>
Reviewed-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>