Move file labeling of '/vendor/bin/ramdump' to non-common path

Since type definition of 'ramdump_exec' locates at non-common path, the
labeling which refers the definition must be living under the same
non-common path.

Bug: 161418316
Test: 'm vendor_file_contexts_test' on git_master & git_master-without-vendor.
Change-Id: I7e2a93fa9527dbe8d3862095c87923407b22cb13
diff --git a/ramdump/file_contexts b/ramdump/file_contexts
new file mode 100644
index 0000000..590e61b
--- /dev/null
+++ b/ramdump/file_contexts
@@ -0,0 +1 @@
+/vendor/bin/ramdump                       u:object_r:ramdump_exec:s0