ARM: imx6: use l2x0 header for register definitions
Instead of using a redundant definition. This makes things a bit cleaner
and also avoids to introduce another private define in the next patch.
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>