ARM: SAMSUNG: Remove remaining uses of plat/regs-timer.h header

This patch removes remaining inclusions of plat/regs-timer.h as
a preparation to remove the header.

As a part of this, things like save and restore of PWM registers are
removed from SoC-specific code, because it is handled in appropriate
drivers now.

Signed-off-by: Tomasz Figa <tomasz.figa@gmail.com>
Reviewed-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Tested-by: Mark Brown <broonie@linaro.org>
Tested-by: Sylwester Nawrocki <sylvester.nawrocki@gmail.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>