mpc8568: Double local bus clock divider

The clock divider for the MPC8568 local bus should be doubled, like the
other newer MPC85xx chips.

Since there are now more chips with a 2x divider than a 1x, and any new
85xx chips will probably be 2x, invert the sense of the #if so that it
lists the 1x chips instead of the 2x ones.

Signed-off-by: Trent Piepho <tpiepho@freescale.com>
Acked-by: Kumar Gala <galak@kernel.crashing.org>
Acked-by: Jon Loeliger <jdl@freescale.com>