serial: samsung: merge probe() function from all SoC specific extensions

With reset port, set clock and get clock functions in SoC specific extentions
being removed, only the driver probe is left over in these extensions. The
probe function itself can be merged into one and moved into the samsung common
serial driver. With driver probe also moved, all the SoC specific extentions
are no longer required and they are deleted.

Cc: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Thomas Abraham <thomas.abraham@linaro.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>