This doesn't do anything more than the clean target, but having both
clean and distclean targets in all makefiles makes standardizing the
cleaning routines easier.
Change-Id: I41578de371a8f767ee23266c30e65e928f0985c4
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/13939
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Tested-by: build bot (Jenkins)
c3fbda4e73