tcg: simplify !CONFIG_TCG handling of tb_invalidate_*

There is no need for a stub, since tb_invalidate_phys_addr can be excised
altogether when TCG is disabled.  This is a bit cleaner since it avoids
using code that is clearly specific to user-mode emulation (it calls
mmap_lock/unlock) for the !CONFIG_TCG case.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

exec.c

@@ -1027,7 +1027,7 @@ const char *parse_cpu_model(const char *cpu_model)
     return cpu_type;
 }
 
-#if defined(CONFIG_USER_ONLY) || !defined(CONFIG_TCG)
+#if defined(CONFIG_USER_ONLY)
 void tb_invalidate_phys_addr(target_ulong addr)
 {
     mmap_lock();
@@ -1046,6 +1046,10 @@ void tb_invalidate_phys_addr(AddressSpace *as, hwaddr addr, MemTxAttrs attrs)
     MemoryRegion *mr;
     hwaddr l = 1;
 
+    if (!tcg_enabled()) {
+        return;
+    }
+
     rcu_read_lock();
     mr = address_space_translate(as, addr, &addr, &l, false, attrs);
     if (!(memory_region_is_ram(mr)