refactor(imx8mp): make use of setup_page_tables()

No functional change. Use the setup_page_tables() helper function which
does the three calls for us. Also the function has some logging support
which will be nice during debugging.

Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
Change-Id: I350965414939865220f745ef5b24d2cdc3095e7b