f2fs: don't call fscrypt_get_encryption_info() explicitly in f2fs_tmpfile()

In f2fs_tmpfile(), parent inode's encryption info is only used when
inheriting encryption context to its child inode, however, we have
already called fscrypt_get_encryption_info() in fscrypt_inherit_context()
to get the encryption info, so just removing unneeded one in
f2fs_tmpfile().

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>