clean-for-rebuild: also remove images_installed stamp

Without this, a linux-rebuild or bootloader-rebuild will not install
the rebuilt image in the images directory.

Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Acked-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/Makefile.package.in

@@ -603,6 +603,7 @@ endif
 			rm -f $$($(2)_TARGET_BUILD)
 			rm -f $$($(2)_TARGET_INSTALL_STAGING)
 			rm -f $$($(2)_TARGET_INSTALL_TARGET)
+			rm -f $$($(2)_TARGET_INSTALL_IMAGES)
 			rm -f $$($(2)_TARGET_INSTALL_HOST)
 
 $(1)-rebuild:		$(1)-clean-for-rebuild all