cscope: do not exclude generated files

The build directory contains some generated source files, such as
include/generated/conf.h, core/include/generated/arm32_sysreg.{h,S} and
core/include/generated/asm-defines.h. Let cscope parse them and only
exclude the files that are copied into the export-ta_* directories (TA
dev kit).

Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Acked-by: Jens Wiklander <jens.wiklander@linaro.org>
diff --git a/Makefile b/Makefile
index 7cad3a9..7ab5f12 100644
--- a/Makefile
+++ b/Makefile
@@ -105,7 +105,7 @@
 cscope:
 	@echo '  CSCOPE  .'
 	${q}rm -f cscope.*
-	${q}find $(PWD) -name "*.[chSs]" | grep -v "$(PWD)/out" > cscope.files
+	${q}find $(PWD) -name "*.[chSs]" | grep -v export-ta_ > cscope.files
 	${q}cscope -b -q -k
 
 .PHONY: checkpatch checkpatch-staging checkpatch-working