target/nios2: Pass semihosting arg to exit

Instead of using R_ARG0 (the semihost function number), use R_ARG1
(the provided exit status).

Signed-off-by: Keith Packard <keithp@keithp.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20230801152245.332749-1-keithp@keithp.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>

target/nios2/nios2-semi.c

@@ -133,8 +133,8 @@ void do_nios2_semihosting(CPUNios2State *env)
     args = env->regs[R_ARG1];
     switch (nr) {
     case HOSTED_EXIT:
-        gdb_exit(env->regs[R_ARG0]);
-        exit(env->regs[R_ARG0]);
+        gdb_exit(env->regs[R_ARG1]);
+        exit(env->regs[R_ARG1]);
 
     case HOSTED_OPEN:
         GET_ARG(0);