exec: Remove MemoryRegion::global_locking field

Last uses of memory_region_clear_global_locking() have been
removed in commit 7070e085d4 ("acpi: mark PMTIMER as unlocked")
and commit 08565552f7 ("cputlb: Move NOTDIRTY handling from I/O
path to TLB path").
Remove memory_region_clear_global_locking() and the now unused
'global_locking' field in MemoryRegion.

Reported-by: Alexander Bulekov <alxndr@bu.edu>
Suggested-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20200806150726.962-1-philmd@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/accel/tcg/cputlb.c b/accel/tcg/cputlb.c
index aaf8e46..2bbbb3a 100644
--- a/accel/tcg/cputlb.c
+++ b/accel/tcg/cputlb.c
@@ -1053,7 +1053,7 @@
         cpu_io_recompile(cpu, retaddr);
     }
 
-    if (mr->global_locking && !qemu_mutex_iothread_locked()) {
+    if (!qemu_mutex_iothread_locked()) {
         qemu_mutex_lock_iothread();
         locked = true;
     }
@@ -1114,7 +1114,7 @@
      */
     save_iotlb_data(cpu, iotlbentry->addr, section, mr_offset);
 
-    if (mr->global_locking && !qemu_mutex_iothread_locked()) {
+    if (!qemu_mutex_iothread_locked()) {
         qemu_mutex_lock_iothread();
         locked = true;
     }