f2fs: remove unneeded check condition in __f2fs_setxattr()

[ Upstream commit bc3994ffa4cf23f55171943c713366132c3ff45d ]

It has checked return value of write_all_xattrs(), remove unneeded
following check condition.

Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Stable-dep-of: aaf8c0b9ae04 ("f2fs: reduce expensive checkpoint trigger frequency")
Signed-off-by: Sasha Levin <sashal@kernel.org>