rtc: stmp3xxx: use stmp_reset_block() instead

The function stmp_reset_block() provides the exactly same functionality
as mxs_reset_block().  So use stmp_reset_block() instead, so that
<mach/common.h> inclusion can be removed.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: rtc-linux@googlegroups.com