[ARM] S3C: Update time initialisation to fix S3C64XX time problems

The S3C64XX timer is running at the wrong rate due to the
assumptions made in the timer initialisation about the way
the pwm dividers work. This means that time on the S3C64XX
runs twice as fast as it should.

Fix the problem by moving to using the clk framework to setup
the pwm timer clock muxes, as the pwm-clock code has all the
necessary knowledge of how the timer clock inputs are routed.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>