Oliver Endriss spotted, that resetting read and write pointers on
flush() requires additional locking and breaks the av7110 driver.
Therefore this patch partially reverts the previous patch titled "make
dvb_ringbuffer compatible to dmxdev_buffer".
Signed-off-by: NAndreas Oberritter <obi@linuxtv.org>
Signed-off-by: NMauro Carvalho Chehab <mchehab@infradead.org>