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/lib/hardwaremain.c

@@ -38,7 +38,6 @@
 #include <arch/acpi.h>
 #endif
 #include <cbmem.h>
-#include <coverage.h>
 #include <timestamp.h>
 
 #if BOOT_STATE_DEBUG
@@ -331,10 +330,6 @@ void hardwaremain(int boot_complete)
 	timestamp_stash(TS_START_RAMSTAGE);
 	post_code(POST_ENTRY_RAMSTAGE);
 
-#if CONFIG_COVERAGE
-	coverage_init();
-#endif
-
 	/* console_init() MUST PRECEDE ALL printk()! */
 	console_init();