clocksource/drivers/samsung_pwm: Cleanup on init error

Failure of timer initialization is likely to be fatal for the system, so
cleanup in such case is not strictly necessary.  However the code might
be refactored or reused, so better not to rely on such assumption that
system won't continue init failure.

Unmap the IO memory and put the clock on initialization failures from
devicetree.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20210506202729.157260-3-krzysztof.kozlowski@canonical.com