cifsd: fix WARNING: Possible unnecessary 'out of memory' message

WARNING: Possible unnecessary 'out of memory' message
902: FILE: fs/cifsd/smb2pdu.c:569:
+       if (!work->response_buf) {
+               ksmbd_err("Failed to allocate %zu bytes buffer\n", sz);

Fix a warning from checkpatch.pl.

Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Steve French <stfrench@microsoft.com>