arm: Update a stale comment in bootblock .S files

arm: Update a stale comment in bootblock .S files

This just updates a comment which refers to "board_init_f". We use
bootblock main() in coreboot.

Change-Id: I4cb6b3c11f163b67fe48de495d13dce88710efc0
Reviewed-on: https://chromium-review.googlesource.com/172095
Reviewed-by: Gabe Black <gabeblack@chromium.org>
Commit-Queue: David Hendricks <dhendrix@chromium.org>
Tested-by: David Hendricks <dhendrix@chromium.org>
(cherry picked from commit 65139f29682cedca8dfb58b3dfe67eab64299064)
Signed-off-by: Isaac Christensen <isaac.christensen@se-eng.com>
Reviewed-on: http://review.coreboot.org/6791
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Tested-by: build bot (Jenkins)