Make the number of DMA buffers and their size configurable using module
parameters. Being able to set these to a higher number might help on
busy systems when handling overall high data rates without having to
edit the driver sources and recompile things.

Picked up from the upstream dddvb-0.9.33 release.
Signed-off-by: Daniel Scheller <d.scheller@gmx.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>