kbuild: remove redundant $(wildcard ...) for cmd_files calculation

I do not see any reason why $(wildcard ...) needs to be called twice
for computing cmd_files.  Remove the first one.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/scripts/Makefile.headersinst b/scripts/Makefile.headersinst
index 5692d7a..c6fb2b7 100644
--- a/scripts/Makefile.headersinst
+++ b/scripts/Makefile.headersinst
@@ -114,9 +114,8 @@
 
 endif
 
-targets := $(wildcard $(sort $(targets)))
 cmd_files := $(wildcard \
-             $(foreach f,$(targets),$(dir $(f)).$(notdir $(f)).cmd))
+             $(foreach f,$(sort $(targets)),$(dir $(f)).$(notdir $(f)).cmd))
 
 ifneq ($(cmd_files),)
 	include $(cmd_files)