rtc: do not use container_of macro as an argument for to_platform_device

The to_platform_device macro itself uses container_of macro.  Nested use
of container_of macro causes following sparse warnings:

rtc-ds1553.c:259:3: warning: symbol '__mptr' shadows an earlier one
rtc-ds1553.c:259:3: originally declared here

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Cc: Alessandro Zummo <alessandro.zummo@towertech.it>
Cc: David Brownell <david-b@pacbell.net>
Cc: Andrew Sharp <andy.sharp@lsi.com>
Cc: Thomas Hommel <thomas.hommel@gefanuc.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>