cpufreq: Fix build of s3c64xx cpufreq driver for header change

The header change has removed an implicit include of module.h, breaking
the build due to the use of THIS_MODULE. Fix that.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>