[media] au0828-input: Be sure that IR is enabled at polling

When the DVB code sets the frontend, it disables the IR
INT, probably due to some hardware bug, as there's no code
there at au8522 frontend that writes on register 0xe0.

Fixing it at au8522 code is hard, as it doesn't know if the
IR is enabled or disabled, and just restoring the value of
register 0xe0 could cause other nasty effects. So, better
to add a hack at au0828-input polling interval to enable int,
if disabled.

Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>