drivers/rtc/rtc-armada38x.c: remove unused local `flags'

Reported-by: Fengguang Wu <fengguang.wu@gmail.com>
Cc: Gregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>