[ARM] 3359/1: S3C24XX - add support for clk_set_rate

Patch from Ben Dooks

Add support for clk_set_rate and clk_round_rate to the
s3c2410 clock implementation

Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>