imx_drm: ipu_v3: fix invalid free of devm_* allocated data

The objects allocated by devm_* APIs are managed by devres and are freed
when the device is detached. There is no need to use kfree() explicitly.

Signed-off-by: Silviu-Mihai Popescu <silviupopescu1990@gmail.com>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>