ksmbd: use kzalloc() instead of __GFP_ZERO

[ Upstream commit f87d4f85

 ]

Use kzalloc() instead of __GFP_ZERO.

Reported-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>