smb: client: get rid of bounds check in SMB2_ioctl_init()

smb2_set_next_command() no longer squashes request iovs into a single
iov, so the bounds check can be dropped.

Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Paulo Alcantara (Red Hat) <pc@manguebit.com>
Signed-off-by: Steve French <stfrench@microsoft.com>