Remove include/private/canned_fs_config.h

canned_fs_config.h should be included as part of libcutils, not as a
global include.  It looks like the few users of this file already do
this correctly, so it's time to remove the symlink.

Test: treehugger
Change-Id: I72d327c2f1f374a1fa9e22b5ee1cceb0311a6818