semihosting: Move user-only implementation out-of-line

Avoid testing CONFIG_USER_ONLY in semihost.h.
The only function that's required is semihosting_enabled.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

semihosting/stubs-all.c

@@ -11,6 +11,12 @@
 #include "qemu/osdep.h"
 #include "semihosting/semihost.h"
 
+/* Queries to config status default to off */
+bool semihosting_enabled(bool is_user)
+{
+    return false;
+}
+
 SemihostingTarget semihosting_get_target(void)
 {
     return SEMIHOSTING_TARGET_AUTO;