[media] dvb_usb_v2: switch interruptible mutex to normal

Fixes error: dvb_usb_v2: pid_filter() failed=-4

error code -4 is EINTR, Interrupted system call

That error blocks I/O in some cases as -EINTR error was returned
by the mutex which was protecting USB control messages. We want
configure hardware to sleep mode on every case after tuning is
stopped. That kind of behavior blocks it, leaving hardware some
unwanted state in worst case.

That error was seen every time when af9015 was plugged to USB1.1
which leads use of hardware PID filters. Stop tuning (tzap) with
ctrl+c failed as driver tries to remove hardware PID filters.

Tested with every hardware which uses routine in question.

Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>