ARM: SAMSUNG: Consolidate plat/pwm-clock.h

Removed
 - arch/arm/plat-s3c24xx/include/mach/pwm-clock.h
 - arch/arm/mach-s3c64xx/include/mach/pwm-clock.h
 - arch/arm/mach-s5p64x0/include/mach/pwm-clock.h
 - arch/arm/mach-s5pc100/include/mach/pwm-clock.h
 - arch/arm/mach-s5pv210/include/mach/pwm-clock.h
 - arch/arm/mach-exynos4/include/mach/pwm-clock.h

And created
 - arch/arm/plat-samsung/include/plat/pwm-clock.h

Cc: Ben Dooks <ben-linux@fluff.org>
[kgene.kim@samsung.com: changed title]
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>