pinctrl: exynos: Refactor handling the pin related dt properties

All pin related dt properties (pin-function, pin-pud and pin-drv) are
handled in a very similar way. Get rid of that code duplication by
extracting the corresponding data knowledge into an actual data
structure (array), and then just iterating over it.

No functional change, it's a refactoring commit.

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>