[CPUFREQ] exynos4210: make needlessly global symbols static

The following symbols are needlessly defined global:
  exynos4_verify_speed
  exynos4_getspeed
  exynos4_set_clkdiv

Make them static.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked-by: Kukjin Kim <kgene.kim@samsung.com>
Signed-off-by: Dave Jones <davej@redhat.com>