MAINTAINERS: Mark some staging directories as "Obsolete"

Several staging directories have TODO files that indicate a
subsystem will be removed in the future.

Using a status entry of "S:	Obsolete" helps indicate the
subsystem files should not be modified unnecessarily.

checkpatch also tests this setting and emits a warning that
the matching subsystem files should not be modified.

This might help avoid receiving patches that will be dropped.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>