tests: arm_thread_swap_tx: nucleo_l552ze_q: Update flash partition

Due to a recent change in TFM, some more space should be allocated
to mcuboot flash partition (some space should be allocated for OTP)
(Cf commit db07170a34f ("Platform: Allocate space in flash for OTP")
in trusted-firmware-m repo)
Take this into account and increase mcuboot flash partition for
nucleo_l552ze_q_ns target.

Signed-off-by: Sebastian Bøe <sebastian.boe@nordicsemi.no>
1 file changed