[CPUFREQ] EXYNOS4210: cpufreq code is changed for stable working

This patch is modify code for stable working
1. Remove unused register access code
2. Change sequence for frequency changing

Signed-off-by: Jaecheol Lee <jc.lee@samsung.com>
Signed-off-by: Jonghwan Choi <jhbird.choi@samsung.com>
Signed-off-by: Jongpill Lee <boyko.lee@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>
Signed-off-by: Dave Jones <davej@redhat.com>