The TM27 support may define TM27_INTERRUPT_VECTOR_ALTERNATIVE to provide
an alternative software generated interrupt request which is raised by
_TM27_Raise_alternative() and cleared by _TM27_Clear_alternative().
Both functions shall return an RTEMS status code. This interrupt vector
may be used to test the interrupt controller support on targets which do
not provide generic software generated interrupts.
Update #3716.
Use the tm27 support to test a spurious interrupt. This helps to run the
validation test case on targets which have no software interrupt available for
tests (for example riscv/PLIC/CLINT in the SMP configuration).
