rtc: s3c: Remove unnecessary call to disable already disabled clock

At the end of s3c_rtc_probe(), s3c_rtc_disable_clk() being called with rtc
clock already disabled (by s3c_rtc_gettime()), which looks extra and
unnecessary call. Lets clean it up.

Signed-off-by: Alim Akhtar <alim.akhtar@samsung.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Reviewed-by: Pankaj Dubey <pankaj.dubey@samsung.com>
Tested-by: Pankaj Dubey <pankaj.dubey@samsung.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>