rtc-isl1208: use sysfs_{create/remove}_group

Instead of individually creating and removing the sysfs device attribute
files, wrap them in an attribute_group and use
sysfs_{create/remove}_group.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Paul Gortmaker <p_gortmaker@yahoo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>