kbuild: Fix modules_install w/o modules error

I fixed scripts/Makefile.modpost to handle CONFIG_MODULES but no modules
selected, but forgot scripts/Makefile.modinst

(pointed out by akpm)

scripts/Makefile.modinst

@@ -9,7 +9,7 @@ include scripts/Makefile.lib
 
 #
 
-__modules := $(shell cd $(MODVERDIR); cat *.mod)
+__modules := $(shell cat /dev/null $(wildcard $(MODVERDIR)/*.mod))
 modules := $(patsubst %.o,%.ko,$(wildcard $(__modules:.ko=.o)))
 
 ifneq ($(filter-out $(modules),$(__modules)),)