ARM: EXYNOS: Add generic PWM lookup support for SMDK4X12

Generic PWM framework requires that the board setup code
register a static mapping that can be used to match PWM
consumers to providers.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Reviewed-by: <thierry.reding@avionic-design.de>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>