arch: arm: improve fault dump for secure firmware

This commit partially reworks the fault dump implementation
of faults in non-secure state that target Secure state. In
particular, the return address to secure state is logged along
with the non-secure address which caused the non-secure fault
(that targets the Secure state).

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