Properly Treble-ize tmpfs access

This is being done in preparation for the migration from ashmem to
memfd. In order for tmpfs objects to be usable across the Treble
boundary, they need to be declared in public policy whereas, they're
currently all declared in private policy as part of the
tmpfs_domain() macro. Remove the type declaration from the
macro, and remove tmpfs_domain() from the init_daemon_domain() macro
to avoid having to declare the *_tmpfs types for all init launched
domains. tmpfs is mostly used by apps and the media frameworks.

Bug: 122854450
Test: Boot Taimen and blueline. Watch videos, make phone calls, browse
internet, send text, install angry birds...play angry birds, keep
playing angry birds...

Change-Id: I20a47d2bb22e61b16187015c7bc7ca10accf6358