Aparently 9865 uses standard BAR encoding scheme (unlike 99xx cards).
Current pci_netmos_9900_setup() uses wrong BAR indices for the 9865 PCI
device, function 2. Using standard BAR indices makes all 6 ports work
for me. Thus disable the NetMos 9900 quirk for NetMos 9865 pci device.

For the reference, here is the relevant part of lspci for my device:

02:07.0 Serial controller: MosChip Semiconductor Technology Ltd. PCI
9865 Multi-I/O Controller (prog-if 02 [16550])
	Subsystem: Device a000:1000
	Flags: bus master, medium devsel, latency 32, IRQ 17
	I/O ports at ac00 [size=8]
	Memory at fcfff000 (32-bit, non-prefetchable) [size=4K]
	Memory at fcffe000 (32-bit, non-prefetchable) [size=4K]
	Capabilities: [48] Power Management version 2
	Kernel driver in use: serial

02:07.1 Serial controller: MosChip Semiconductor Technology Ltd. PCI
9865 Multi-I/O Controller (prog-if 02 [16550])
	Subsystem: Device a000:1000
	Flags: bus master, medium devsel, latency 32, IRQ 18
	I/O ports at a800 [size=8]
	Memory at fcffd000 (32-bit, non-prefetchable) [size=4K]
	Memory at fcffc000 (32-bit, non-prefetchable) [size=4K]
	Capabilities: [48] Power Management version 2
	Kernel driver in use: serial

02:07.2 Communication controller: MosChip Semiconductor Technology Ltd.
PCI 9865 Multi-I/O Controller
	Subsystem: Device a000:3004
	Flags: bus master, medium devsel, latency 32, IRQ 19
	I/O ports at a400 [size=8]
	I/O ports at a000 [size=8]
	I/O ports at 9c00 [size=8]
	I/O ports at 9800 [size=8]
	Memory at fcffb000 (32-bit, non-prefetchable) [size=4K]
	Capabilities: [48] Power Management version 2
	Kernel driver in use: serial

Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>