Merge pull request #1070 from riscv/trigger_priority

Triggers with action != 0 or 1 fire independently.

Sdtrig.adoc

@@ -141,9 +141,10 @@ and that a trigger set by user code doesn't affect the external
 debugger. If this is not implemented, then the hart must enter Debug
 Mode and ignore the breakpoint exception. In the latter case, {mcontrol-hit} of the
 trigger whose action is 0 must still be set, giving a debugger an
-opportunity to handle this case. What happens with trace actions when
-triggers with different actions are also firing is left to the trace
-specification.
+opportunity to handle this case.
+Since triggers that have an action other than 0 or 1 don't affect the execution
+of the hart, they are not mentioned in the priority table. Such triggers fire
+independently from those that have an action of 0 or 1.
 
 [[nativetrigger]]
 === Native Triggers