kbuild: modinst: read modules.order instead of $(MODVERDIR)/*.mod

Towards the goal of removing MODVERDIR, read out modules.order to get
the list of modules to be installed. This is simpler than parsing *.mod
files in $(MODVERDIR).

For external modules, $(KBUILD_EXTMOD)/modules.order should be read.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

scripts/Makefile.modinst

@@ -8,10 +8,7 @@ __modinst:
 
 include scripts/Kbuild.include
 
-#
-
-__modules := $(sort $(shell grep -h '\.ko$$' /dev/null $(wildcard $(MODVERDIR)/*.mod)))
-modules := $(patsubst %.o,%.ko,$(wildcard $(__modules:.ko=.o)))
+modules := $(sort $(shell cat $(if $(KBUILD_EXTMOD),$(KBUILD_EXTMOD)/)modules.order))
 
 PHONY += $(modules)
 __modinst: $(modules)