modules: tf-m: allow DOWNLOAD option for mcuboot

Allow developers the option of using the DOWNLOAD option
for MCUboot in TF-M bulds with BL2. Using MCUboot from
Zephyr is still the default option.

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>
2 files changed