usb: chipidea: imx: Cleanup ci_hdrc_imx_platform_flag

Some trivial cleanups, that do not change functionality.

Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Signed-off-by: Peter Chen <peter.chen@nxp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>