V4L/DVB (6700): pvrusb2: Soften the crashed encoder warning message

The pvrusb2 driver has been successfully recovering from a crashed
encoder now for over 2 years.  I think it's time to reduce the
perceived severity of the warning message.  While I'd still very much
like to stop these crashes, the recovery logic is solid enough that
the problem is effectively benign.  No point in panicing the users
over it.

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