net: dsa: sja1105: Switch to hardware operations for PTP

Adjusting the hardware clock (PTPCLKVAL, PTPCLKADD, PTPCLKRATE) is a
requirement for the auxiliary PTP functionality of the switch
(TTEthernet, PPS input, PPS output).

Therefore we need to switch to using these registers to keep a
synchronized time in hardware, instead of the timecounter/cyclecounter
implementation, which is reliant on the free-running PTPTSCLK.

Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>