ARM: mx5: Use common function for configuring AIPS

Now that a common imx_set_aips() function is available, use it on mx51 and mx53.

This lets the code smaller and cleaner.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>