arm64: dts: hisi: add refclk node to hip06 dts files for SAS

We will only maintain 1 dts for D03 and there are 50MHz
and 66MHz versions of D03: so we expect UEFI to update
refclk rate in the fdt at boot time.

Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Xiang Chen <chenxiang66@hisilicon.com>
Signed-off-by: Wei Xu <xuwei5@hisilicon.com>