gitignore: Adding rule to ignore cscope files.

Change-Id: I2f7c9d0ccb80e0446ffee0360c5bc6d3e4e54111
diff --git a/.gitignore b/.gitignore
index a0c5437..2b8af71 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,3 +5,8 @@
 TAGS
 local.mk
 target/*/tools/mkheader
+
+# cscope files
+cscope.*
+ncscope.*
+