octeontx2-af: Use ptp input clock info from firmware data

The input clock frequency of PTP block is figured
out from hardware reset block currently. The firmware
data already has this info in sclk. Hence simplify
ptp driver to use sclk from firmware data.

Signed-off-by: Subbaraya Sundeep <sbhatta@marvell.com>
Signed-off-by: Hariprasad Kelam <hkelam@marvell.com>
Signed-off-by: Sunil Goutham <sgoutham@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>