Replace SERIAL_CPU_INIT with PARALLEL_CPU_INIT

Lines with 'select SERIAL_CPU_INIT' where redundant with the
default being yes. Since there is no 'unselect SERIAL_CPU_INIT'
possibility, invert the default and rename option.

This squelches Kconfig warnings about unmet dependencies.

Change-Id: Iae546c56006278489ebae10f2daa627af48abe94
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/5700
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>