In the Cortex-M exception table we rename z_arm_reserved()
function to z_arm_exc_spurious(), as it is invoked when
existing (that is, non-reserved) but un-installed exceptions
are triggered, accidentaly, by software, or hardware. This
currently applies to SysTick and SecureFault exceptions.
Since fault.S is shared between Cortex-M and other AARCH32
architectures, we keep z_arm_reserved as a defined symbol
there. This commit does some additional, minor, "no-op"
cleanup in #ifdef's for Cortex-M and Cortex-R.
Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>