drivers/rtc/rtc-ds3234.c: fix whitespace issue

Fixes the following warning:

  WARNING: please, no space before tabs
Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Cc: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>