platform: nordic_nrf: Add ifdef for peripheral mmio region structs

Add ifdef for peripheral MMIO region structs to make sure that they
are not included in the build when they aren't required to be configured
as secure peripherals.

Change-Id: I1fac0ed7d5555eff10b7a134b4bded6eb9044d87
Signed-off-by: Joakim Andersson <joakim.andersson@nordicsemi.no>
1 file changed