Add mainboard hook to bootblock

Change allows to override default bootblock_mainboard_init() with
mainboard-specific code.

If the default bootblock_mainboard_init() handler is replaced, with
one from file BOOTBLOCK_MAINBOARD_INIT, one needs to take care the
replacement calls all the necessary bootblock_x_init() functions.

Change-Id: Ie8c667cdba7cafe9ed2d4b19ab2bd21d941ad4ca
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/1845
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
2 files changed