media: ir-kbd-i2c: convert to i2c_new_dummy_device()

Convert this driver to use the new i2c_new_dummy_device() call and bail
out if the dummy device cannot be registered to make failure more
visible to the user.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>