f2fs: pass flags field to setxattr functions

This patch passes the "flags" field to the low level setxattr functions
to use XATTR_REPLACE in the following patches.

Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

diff --cc fs/f2fs/acl.c
Simple merge

diff --cc fs/f2fs/xattr.c
Simple merge

diff --cc fs/f2fs/xattr.h
Simple merge