V4L/DVB (13224): pvrusb2: Improve diagnostic info on driver initialization failure

It used to be that the only real detectable reason for the driver to
fail during initialization would be that if the hardware is simply
jammed.  However with the advent of the sub-device mechanism in V4L it
is possible now to detect if a sub-device module fails to load
successfully.  The pvrusb2 driver does in fact react to this by also
(correctly) failing, however the original diagnostic message "hardware
is jammed" was still being reported.  This misleads the user because
in fact it might not actually be a hardware failure.  This change adds
logic to tell the difference and then report a more appropriate
message to the kernel log.

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