PCI: layerscape: Fix MSG TLP drop setting

commit 1195c103 upstream.

Some kinds of Layerscape PCIe controllers will forward the received message
TLPs to system application address space, which could corrupt system memory
or lead to a system hang.  Enable MSG_DROP to fix this issue.

Signed-off-by: Minghuan Lian <Minghuan.Lian@nxp.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Matthias Brugger <mbrugger@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>