V4L/DVB (11850): pvrusb2: Instantiate ir_video I2C device by default

Now that the ir-kbd-i2c driver has been converted to a new-style i2c
driver, we can instantiate the ir_video I2C device by default. The
pvr2_disable_ir_video is kept to disable the IR receiver, either
because the user doesn't use it, or for debugging purpose.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Acked-by: Mike Isely <isely@pobox.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>