V4L/DVB (12940): SAA7164: IRQ / message timeout related change

In some cases we're seeing large timeouts on commands. I'm changing the
implementation so that the deferred worker checks the PCI bus for
any messages and signals the waiting caller accordingly. The previous
mechanism was too unreliable.

Signed-off-by: Steven Toth <stoth@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>