Replace hlt() loops with halt()

Change-Id: I8486e70615f4c404a342cb86963b5357a934c41d
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-on: http://review.coreboot.org/7606
Tested-by: build bot (Jenkins)
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
25 files changed