V4L/DVB (4676): Dynamic cx88 mpeg port management for HVR1300 MPEG2/DVB-T support.

A series of patches to change the cx88 framework to allow the
PCI mpeg port to be shared dynamically between different
types of drivers or applications. This patch changes the cx88-dvb
and cx88-blackbird drivers to become 'sub drivers' of a higher
single cx88-mpeg driver.
The cx88-mpeg driver is a superset of the previous cx88-mpeg/blackbird
drivers and now owns the IRQ. cx88-dvb/blackbird now become mini drivers,
registering themselves with cx88-mpeg through a standard interface with
callbacks.
Sub drivers request access to hardware via the cx88-mpeg driver. In turn
the cx88-mpeg driver determines whether the hardware is busy and accepts
or refuses the request, grant access using callbacks into the sub drivers.
The net effect is that you are no longer able to tamper with the mpeg port
from multiple different applications at the same time, potentially breaking
a live mpeg2 hardware encoding or dvb stream.
The mechanism extends to enable multiple dvb frontends to be registered
and share the single resource.

Signed-off-by: Steven Toth <stoth@hauppauge.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>