init.rc: tune F2FS to be aligned to system settings

Android sets /proc/sys/vm/dirty_expire_centisecs to 200, so f2fs
doesn't need to do checkpoint in 60 seconds.

Bug: 127511432
Change-Id: I2ba0623053d4480b82003eb1cca85ff03c61fc0f
Signed-off-by: Jaegeuk Kim <jaegeuk@google.com>