Implement poll() method for debugfs and be sure that the
debug_data won't be freed on ir or on read().
With this change, poll() will return POLLIN if either data was
filled or if data was read. That allows read() to return 0
to indicate EOF in the latter case.
As poll() is now provided, fix support for non-block mode.
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

Those fields help to identify the version of the ISDB stats.
Useful while debuging the driver.
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

To avoid mixing two different things at the same place, move the
debugfs code into a separate file.
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>