V4L/DVB: pvrusb2: Reduce encoder quiet period

After implementing a 300msec wait between digitizer start and encoder
start, it has been determined that we don't need to wait quite as long
before configuring the encoder.  This reduces the wait period from
100msec back to 50msec.

Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>