ARM: S3C24XX: cpufreq-utils: don't write raw values to MPLLCON when using ccf

The s3c24xx cpufreq driver needs to change the mpll speed and was doing
this by writing raw values from a translation table into the MPLLCON
register.

Change this to use a regular clk_set_rate call when using the common
clock framework and only write the raw value in the samsung_clock case.

The s3c cpufreq driver does already aquire the mpll, so simply add a reference
to struct s3c_cpufreq_config to let set_fvco access it.

While struct clk is opaque the differenciation between samsung clock and
common clock is kept, as the samsung-clock mpll clk does not implement a
real set_rate.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>