clk: qoriq: Don't allow CPU clocks higher than starting value

The boot-time frequency of a CPU is considered its rated maximum, as we
have no other source of such information.  However, this was previously
only used for chips with 80% restrictions on secondary PLLs.  This
usually wasn't a problem because most chips/configs boot with a divider
of /1, with other dividers being used only for dynamic frequency
reduction.  However, at least one config (LS1021A at less than 1 GHz)
uses a different divider for top speed.  This was causing cpufreq to set
a frequency beyond the chip's rated speed.

This is fixed by applying a 100%-of-initial-speed limit to all CPU PLLs,
similar to the existing 80% limit that only applied to some.

Signed-off-by: Scott Wood <oss@buserror.net>
Cc: stable@vger.kernel.org
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>