configure: We don't want to clean configuration files

If you don't want to compile everything, you configure
config-devices.mak.  And then make clean remove it, and make will
create a default one without your configuration.  Fix it by not
removing it on clean target.  Remove it instead on distclean.
Signed-off-by: NJuan Quintela <quintela@redhat.com>
Reviewed-by: NThomas Huth <thuth@redhat.com>

---

Remove it instead on distclean.

Makefile

@@ -752,7 +752,7 @@ clean:
 	if test -d $$d; then $(MAKE) -C $$d $@ || exit 1; fi; \
 	rm -f $$d/qemu-options.def; \
         done
-	rm -f $(SUBDIR_DEVICES_MAK) config-all-devices.mak
+	rm -f config-all-devices.mak
 
 VERSION ?= $(shell cat VERSION)
 
@@ -764,6 +764,7 @@ qemu-%.tar.bz2:
 distclean: clean
 	rm -f config-host.mak config-host.h* config-host.ld $(DOCS) qemu-options.texi qemu-img-cmds.texi qemu-monitor.texi qemu-monitor-info.texi
 	rm -f config-all-devices.mak config-all-disas.mak config.status
+	rm -f $(SUBDIR_DEVICES_MAK)
 	rm -f po/*.mo tests/qemu-iotests/common.env
 	rm -f roms/seabios/config.mak roms/vgabios/config.mak
 	rm -f qemu-doc.info qemu-doc.aux qemu-doc.cp qemu-doc.cps