cpufreq: s3c24xx: Remove some dead code

There is no use for the .resume_clocks() callback now and in fact all
the provided functions are empty, so this patch just removes it in
preparation for further patches.

Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>