ARM: s3c24xx: pass pointer to clk driver via platform data

Passing pointers directly as platform data is fragile and undocumented.
Better to create a platform data structure which explicitly documents
what is passed to the driver.

Suggested-by: Tomasz Figa <tomasz.figa@gmail.com>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lore.kernel.org/r/20200806182059.2431-6-krzk@kernel.org