coverage: use boot state callbacks

Utilize the static boot state callback scheduling to initialize
and tear down the coverage infrastructure at the appropriate points.
The coverage initialization is performed at BS_PRE_DEVICE which is the
earliest point a callback can be called. The tear down occurs at the
2 exit points of ramstage: OS resume and payload boot.

Change-Id: Ie5ee51268e1f473f98fa517710a266e38dc01b6d
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/3135
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

src/include/coverage.h

@@ -1,21 +0,0 @@
-/*
- * This file is part of the coreboot project.
- *
- * Copyright (C) 2012 Google, Inc.
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; version 2 of the License.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA, 02110-1301 USA
- */
-
-void coverage_init(void);
-void coverage_exit(void);