linux-user: stack_base is now mandatory on all targets

Signed-off-by: NRiku Voipio <riku.voipio@linaro.org>

linux-user/qemu.h

@@ -123,10 +123,10 @@ typedef struct TaskState {
 #endif
 #if defined(TARGET_ARM) || defined(TARGET_M68K) || defined(TARGET_UNICORE32)
     /* Extra fields for semihosted binaries.  */
-    uint32_t stack_base;
     uint32_t heap_base;
     uint32_t heap_limit;
 #endif
+    uint32_t stack_base;
     int used; /* non zero if used */
     struct image_info *info;
     struct linux_binprm *bprm;