arch_topology: Fix putting invalid cpu clk

Add a sanity check before putting the cpu clk.

Fixes: b8fe128d

 (“arch_topology: Adjust initial CPU capacities with current freq")
Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
Link: https://lore.kernel.org/r/20200317063308.23209-1-jeffy.chen@rock-chips.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>