clk: at91: sama7g5: decrease lower limit for MCK0 rate

On SAMA7G5 CPU clock is changed at run-time by DVFS. Since MCK0 and
CPU clock shares the same parent clock (CPUPLL clock) the MCK0 is
also changed by DVFS to avoid over/under clocking of MCK0 consumers.
The lower limit is changed to be able to set MCK0 accordingly by
DVFS.

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/1605800597-16720-9-git-send-email-claudiu.beznea@microchip.com


Signed-off-by: Stephen Boyd <sboyd@kernel.org>