[media] ir-kbd-i2c: improve remote behavior with z8 behind usb

Add the same "are you ready?" i2c_master_send() poll command to
get_key_haup_xvr found in lirc_zilog, which is apparently seen in
the Windows driver for the PVR-150 w/a z8. This stabilizes what is
received from both the HD-PVR and HVR-1950, even with their polling
intervals at the default of 100, thus the removal of the custom
260ms polling_interval in pvrusb2-i2c-core.c.

Acked-by: Andy Walls <awalls@md.metrocast.net>
Acked-by: Mike Isely <isely@isely.net>
Signed-off-by: Jarod Wilson <jarod@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>