LF-3161-1 arm: imx: Fix speculative instruction prefetch issue

LF-3161-1 arm: imx: Fix speculative instruction prefetch issue

Default ARM32 MMU setting in u-boot sets XN bit to entire 4GB space no
matter which DCACHE option is used, and set domain permission to manager.
This causes MMU ignores the access check and XN bit, so speculative
instruction can fetch from entire space.

This patch sets the DDR, ROM, OCRAM without XN bit, and set domain to client
to enable the XN and access check. So speculative instruction fetch can only
happens on these 3 regions to avoid prefetch from peripherals and invalid
regions.

Signed-off-by: Ye Li <ye.li@nxp.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
(cherry picked from commit 25d70768c460bad91aa65f367203af41122399cd)
(cherry picked from commit 647edf3ae8bb7d48d20155e73a65522ae9e3ad36)