target-xtensa: implement interrupt option

See ISA, 4.4.6 (interrupt option), 4.4.7 (high priority interrupt
option) and 4.4.8 (timer interrupt option) for details.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
diff --git a/target-xtensa/helpers.h b/target-xtensa/helpers.h
index 6e02d26..28689c3 100644
--- a/target-xtensa/helpers.h
+++ b/target-xtensa/helpers.h
@@ -17,4 +17,9 @@
 DEF_HELPER_1(simcall, void, env)
 DEF_HELPER_0(dump_state, void)
 
+DEF_HELPER_2(waiti, void, i32, i32)
+DEF_HELPER_2(timer_irq, void, i32, i32)
+DEF_HELPER_1(advance_ccount, void, i32)
+DEF_HELPER_1(check_interrupts, void, env)
+
 #include "def-helper.h"