[media] em28xx-input: NULL dereference on error

We call "kfree(ir->i2c_client);" in the error handling and that doesn't
work if "ir" is NULL.

Fixes: 78e719a5 ('[media] em28xx-input: i2c IR decoders: improve i2c_client handling')

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Frank Schäfer <fschaefer.oss@googlemail.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>