ANDROID: configfs: add proper module namespace marking

Commit d483eed8 ("ANDROID: GKI: set vfs-only exports into their own
namespace") added a namespace for vfs functions.  For some kernelci
build targets, configfs is built as a module, so add the proper
namespace marking for configfs as well to fix the reported build
problems.

Fixes: d483eed8 ("ANDROID: GKI: set vfs-only exports into their own namespace")
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I1abc2f17d9a8f90f1fe060b314eb69cb1e6cfc5d