clocksource: samsung_pwm_timer: Handle suspend/resume correctly

Current suspend/resume handling of the driver was broken, because:
 - periodic timer was being enabled in CLOCK_EVT_MODE_RESUME mode, which
   does not seem to be correct behavior looking at other platforms,
 - PWM divisors need to be restored, but they were not,
 - clockevent interrupt mask needs to be restored, but it was not,
 - clocksource was being restored in clockevent resume callback.

This patch fixes issues mentioned above, making suspend/resume handling
in the driver correct.

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>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>