This commit implements the architecture specific parts for the
Zephyr tracing subsystem on SPARC and LEON3. It does so by calling
sys_trace_isr_enter(), sys_trace_isr_exit() and sys_trace_idle().
The logic for the ISR tracing is:
1. switch to interrupt stack
2. *call sys_trace_isr_enter()* if CONFIG_TRACING_ISR
3. call the interrupt handler
4. *call sys_trace_isr_exit()* if CONFIG_TRACING_ISR
5. switch back to thread stack
Signed-off-by: Martin Åberg <martin.aberg@gaisler.com>