Bluetooth: hci_core: Fix not checking skb length on hci_acldata_packet

[ Upstream commit 3fe288a8 ]

This fixes not checking if skb really contains an ACL header otherwise
the code may attempt to access some uninitilized/invalid memory past the
valid skb->data.

Reported-by:  <syzbot+6ea290ba76d8c1eb1ac2@syzkaller.appspotmail.com>
Tested-by:  <syzbot+6ea290ba76d8c1eb1ac2@syzkaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=6ea290ba76d8c1eb1ac2


Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>