boards: lpcxpresso55s69 mcuboot and tfm partitions

Moved the flash partitioning to the shared device tree include so all
targets can benefit from the partitioning.
This is implemented to MCUboot can run TFM(S) with Zephyr
(lpc55s69 cpu 0 NS).
Also defines RAM partitions as TFM expects them, first part of ram for
S, second half for NS.

Signed-off-by: Andrei Gansari <andrei.gansari@nxp.com>