MAINTAINERS: add the VFS git tree

The VFS git tree is missing from MAINTAINERS.  Add it.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20240820195109.38906-1-ebiggers@kernel.org


Signed-off-by: Christian Brauner <brauner@kernel.org>