xilinx: r5: Fix MPU setting for R5

Map all resource for R5 to operate properly.
The patch is done based on the commit 23f7b1a7 ("armv7R: K3: am654:
Enable MPU regions") which also map the whole 4GB at first and then change
mapping for DDR.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>