drivers/rtc/rtc-s3c.c: add .needs_src_clk to s3c6410 RTC data

Commit df9e26d0 ("rtc: s3c: add support for RTC of Exynos3250 SoC")
added an "rtc_src" DT property to specify the clock used as a source to
the S3C real-time clock.

Not all SoCs needs this so commit eaf3a659 ("drivers/rtc/rtc-s3c.c:
fix initialization failure without rtc source clock") changed to check
the struct s3c_rtc_data .needs_src_clk to conditionally grab the clock.

But that commit didn't update the data for each IP version so the RTC
broke on the boards that needs a source clock. This is the case of at
least Exynos5250 and Exynos5440 which uses the s3c6410 RTC IP block.

This commit fixes the S3C rtc on the Exynos5250 Snow and Exynos5420
Peach Pit and Pi Chromebooks.

Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Chanwoo Choi <cw00.choi@samsung.com>
Cc: Doug Anderson <dianders@chromium.org>
Cc: Olof Johansson <olof@lixom.net>
Cc: Kevin Hilman <khilman@linaro.org>
Cc: Tyler Baker <tyler.baker@linaro.org>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>