cscope: skip in tree out directory

By default if nothing is specified OP-TEE is built keeping the output under
the directory "out" in the source tree. With this patch the cscope database
will not include those files.

Reviewed-by: Joakim Bech <joakim.bech@linaro.org>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
diff --git a/Makefile b/Makefile
index 069519a..ddd63f1 100644
--- a/Makefile
+++ b/Makefile
@@ -95,5 +95,5 @@
 cscope:
 	@echo '  CSCOPE  .'
 	${q}rm -f cscope.*
-	${q}find $(PWD) -name "*.[chSs]" > cscope.files
+	${q}find $(PWD) -name "*.[chSs]" | grep -v "$(PWD)/out" > cscope.files
 	${q}cscope -b -q -k