arm: mvebu: a38x: serdes: Don't set PCIe Common Clock Configuration

Enabling Common Clock Configuration bit in PCIe Root Port Link Control
Register should not be done unconditionally. It is enabled by operating
system as part of ASPM. Also after enabling Common Clock Configuration it
is required to do more work, like retraining link. Some cards may be broken
due to this incomplete Common Clock Configuration and some cards are broken
and do not support ASPM at all.

Remove this incomplete code for Common Clock Configuration. It really
should not be done in SerDes code as it is not related to SerDes, but to
PCIe subsystem.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Stefan Roese <sr@denx.de>