V4L/DVB (12938): SAA7164: Increase the firmware command timeout to avoid firmware errors.

The firmware typically responds in < 50ms and, via the interrupts and
deferred work queue the caller (blocked in the driver) is signalled very
efficiently. In a highly stressed system this can take many multiples
of seconds. So, we need a larger maximum timeout for busy systems.

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