ARM: s3c24xx: iotiming: make functions static

There are two functions in this file that are never called from
anywhere else, so they should be static to allow the compiler
to optimize it better and not pollute the global namespace.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20200806182059.2431-4-krzk@kernel.org
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>