[media] em28xx: remove i2cdprintk() messages

We don't report any key/scan codes or errors inside the key polling functions
for internal IR RC devices, just in the key handling fucntions.
Do the same for external devices.

Signed-off-by: Frank Schäfer <fschaefer.oss@googlemail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>