hw: move qdev-monitor.o to toplevel directory

qdev-monitor.c is the only "core qdev" file that is not used in
user-mode emulation, and it does not define anything that is used
by hardware models.  Remove it from the hw/ directory and
remove hw/qdev-monitor.h from hw/qdev.h too; this requires
some files to have some new explicitly includes.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/vl.c b/vl.c
index e0a8eeb..bbdbafd 100644
--- a/vl.c
+++ b/vl.c
@@ -126,6 +126,7 @@
 #include "hw/xen.h"
 #include "hw/qdev.h"
 #include "hw/loader.h"
+#include "monitor/qdev.h"
 #include "bt/bt.h"
 #include "net/net.h"
 #include "net/slirp.h"