clk: mvebu: ap806: Fix clock name for the cluster

Actually, the clocks exposed for the cluster are not the CPU clocks, but
the PLL clock used as entry clock for the CPU clocks. The CPU clock will
be managed by a driver submitting in the following patches.

Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>
Link: https://lkml.kernel.org/r/20190710134346.30239-5-gregory.clement@bootlin.com


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