boards: b_u585i_iot02a: Add a non-secure target

Provide a _ns target for b_u585i_iot02a board.
Flash partition is given as default for most applications,
with the following sizes:
MCUBoot: 208K
Secure: 256K
Non secure: 512K

Tested using tfm_ipc sample.

Signed-off-by: Erwan Gouriou <erwan.gouriou@linaro.org>
9 files changed