tcg: mark local temps as MEM in dead_temp()

In dead_temp, local temps should always be marked as back to memory,
even if they have not been allocated (i.e. they are discared before
cross a basic block).

It fixes the following assertion in target-xtensa:

    qemu-system-xtensa: tcg/tcg.c:1665: temp_save: Assertion `s->temps[temp].val_type == 2 || s->temps[temp].fixed_reg' failed.
    Aborted
Reported-by: NMax Filippov <jcmvbkbc@gmail.com>
Tested-by: NMax Filippov <jcmvbkbc@gmail.com>
Signed-off-by: NAurelien Jarno <aurelien@aurel32.net>

tcg/tcg.c

@@ -1615,7 +1615,7 @@ static inline void temp_dead(TCGContext *s, int temp)
         if (ts->val_type == TEMP_VAL_REG) {
             s->reg_to_temp[ts->reg] = -1;
         }
-        if (temp < s->nb_globals || (ts->temp_local && ts->mem_allocated)) {
+        if (temp < s->nb_globals || ts->temp_local) {
             ts->val_type = TEMP_VAL_MEM;
         } else {
             ts->val_type = TEMP_VAL_DEAD;