armv8: fsl-layerscape: Allocate Secure memory from first ddr region

armv8: fsl-layerscape: Allocate Secure memory from first ddr region

This change is required due to trusted OS (OP-TEE) not being position
independent code, it requires compile time fixed base address.

To take care of this it is assumed that all layerscape armv8 platforms
has minimum 2G ddr in first region. So we can have fixed address
space (66 MB -> (2MB for PPA + 64MB for trusted OS)) allocated from
top of first 2G ddr region and compile trusted OS with this fixed
base address.

But one exception here is ls1012 where we have only 1G (rdb) or 512M
(frdm) ddr memory. For those we can have different fixed compile time
base addresses for trusted OS.

Signed-off-by: Sumit Garg <sumit.garg@nxp.com>
Reviewed-by: York Sun <york.sun@nxp.com>