stmmac: intel: Adding ref clock 1us tic for LPI cntr

Adding reference clock (1us tic) for all LPI timer on Intel platforms.
The reference clock is derived from ptp clk. This also enables all LPI
counter.

Signed-off-by: Rusaimi Amira Ruslan <rusaimi.amira.rusaimi@intel.com>
Signed-off-by: Voon Weifeng <weifeng.voon@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>