[ARM] S3C2443: Fix HCLK rate

Fix the calculation of HCLK on the S3C2443, it should not
have been passed through S3C2443_CLKDIV0_HALF_HCLK.

Re-work of original patch from Wei Shuai <cpuwolf@gmail.com>

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