PL BRAM's last KB is designated as non-secure and is accessible only by the APU.
Configure the associated XMPU region as non-secure with Strict Check Type. The APU has
to set the AXI protection security level to non-secure (AxProt[1]=1) to access the region. Since bare metal standalone
applications are being run in this example, all transactions originating from the APU
enters the PL as secure (AxProt[1]=0). Therefore, to
isolate the region to the APU, the region is configured as secure, but only the APU is
authorized to access it.