media: em28xx: Add support for Hauppauge USB QuadHD

Hauppauge USB QuadHD contains two two-tuner em28xx
devices behind a usb hub. Each of the four dvb adapters
contains a MaxLinear 692 combo ATSC demod/tuner.

Bus 003 Device 006: ID 2040:846d Hauppauge
Bus 003 Device 005: ID 2040:846d Hauppauge
Bus 003 Device 004: ID 04e2:0404 Exar Corp.

Signed-off-by: Brad Love <brad@nextdimension.cc>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>