stubs: group all monitor_fdset_* functions in a single file

It makes little sense to implement only one of them, so avoid
proliferation of stubs files.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

stubs/Makefile.objs

@@ -10,10 +10,7 @@ stub-obj-y += cpu-get-clock.o
 stub-obj-y += cpu-get-icount.o
 stub-obj-y += dump.o
 stub-obj-y += error-printf.o
-stub-obj-y += fdset-add-fd.o
-stub-obj-y += fdset-find-fd.o
-stub-obj-y += fdset-get-fd.o
-stub-obj-y += fdset-remove-fd.o
+stub-obj-y += fdset.o
 stub-obj-y += gdbstub.o
 stub-obj-y += get-vm-name.o
 stub-obj-y += iothread.o

stubs/fdset-find-fd.c

-#include "qemu/osdep.h"
-#include "qemu-common.h"
-#include "monitor/monitor.h"
-
-int monitor_fdset_dup_fd_find(int dup_fd)
-{
-    return -1;
-}

stubs/fdset-get-fd.c

-#include "qemu/osdep.h"
-#include "qemu-common.h"
-#include "monitor/monitor.h"
-
-int monitor_fdset_get_fd(int64_t fdset_id, int flags)
-{
-    return -1;
-}

stubs/fdset-remove-fd.c

-#include "qemu/osdep.h"
-#include "qemu-common.h"
-#include "monitor/monitor.h"
-
-void monitor_fdset_dup_fd_remove(int dupfd)
-{
-}

stubs/fdset-add-fd.c → stubs/fdset.c

@@ -6,3 +6,17 @@ int monitor_fdset_dup_fd_add(int64_t fdset_id, int dup_fd)
 {
     return -1;
 }
+
+int monitor_fdset_dup_fd_find(int dup_fd)
+{
+    return -1;
+}
+
+int monitor_fdset_get_fd(int64_t fdset_id, int flags)
+{
+    return -1;
+}
+
+void monitor_fdset_dup_fd_remove(int dupfd)
+{
+}