drivers/rtc/rtc-em3027.c: add device tree support

Set the of_match_table for this driver so that devices can be described in
the device tree.  This device is used in the Trimslice and is already
defined in the Trimslice device tree.

Signed-off-by: Peter Robinson <pbrobinson@gmail.com>
Cc: Mike Rapoport <mike@compulab.co.il>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Grant Likely <grant.likely@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>