net: au1k_ir: Use module_platform_driver()

module_platform_driver macro removes some boilerplate and
simplifies the code.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Cc: Samuel Ortiz <samuel@sortiz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>