execute1: Fix setting HEIR and FSCR[IC] on interrupts

Code in the execute1_actions process that handles illegal and facility
unavailable interrupts was setting actions.se.set_heir or
actions.se.set_ic, but then because actions.exception was also set,
the contents of actions.se were ignored, meaning that HEIR or FSCR[IC]
were not getting updated.  To fix this, execute1_1 now conditions use
of those fields on valid_in rather than go.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

execute1.vhdl

@@ -1747,6 +1747,8 @@ begin
         if valid_in = '1' then
             v.prev_op := e_in.insn_type;
             v.prev_prefixed := e_in.prefixed;
+            v.se.set_heir := actions.se.set_heir;
+            v.se.write_ic := actions.se.write_ic;
         end if;
 
         -- Determine if there is any interrupt to be taken