phytec-imx8m boards: enable OP-TEE for KASLR

phytec-imx8m boards: enable OP-TEE for KASLR

Enable OP-TEE config and RNG by default.
Set OP-TEE load address to end of 1GiB RAM for phycore-imx8mp and
phycore-imx8mm as the boards support a 1GiB RAM variant (although not
yet upstreamed for phycore-imx8mm).
The imx8mm-phygate-tauri-l board only supports 2GiB, so the default at
the end of 2GiB is sufficient.

Reviewed-by: Teresa Remmet <t.remmet@phytec.de>
Signed-off-by: Yannic Moog <y.moog@phytec.de>