powerpc/p2041rdb: updated description of cpld command

According to CPLD 2.2, the default configuration is changed, so updated the
description of CPLD command, otherwise it will confusing.

Signed-off-by: Shaohui Xie <Shaohui.Xie@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>