platform: nordic_nrf: Don't configure TFM_SYSTEM_DSP OFF

preload.cmake should contain platform-specific configuration. But TF-M
does not support TFM_SYSTEM_DSP so it is not necessary to configure it
for each platform.

NB: These platforms do support DSP instructions.

Change-Id: Ifd3a67ac2276fa8d7ceec79582f8cec02b7cac54
Signed-off-by: Sebastian Bøe <sebastian.boe@nordicsemi.no>
3 files changed