libbinder_ndk: allow apex symbols also for vndk.

Vendor code might add or retrieve services with a specific stability
level at some point in the future. Currently, this is prohibited by
SELinux.

Bug: 138152918
Test: use symbols from vendor context
Change-Id: I361676c6e303e2e754ddb3c1b14ebe1e18605d3b
1 file changed