clocksource: exynos_mct: remove platform header dependency

For the non-DT case, the mct_init() function requires access
to a couple of platform specific constants, but cannot include
the header files in case we are building for multiplatform.

This changes the interface to the platform so we pass all
the necessary data as arguments to mct_init.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>