This patch implements PHC (ptp hardware clock) driver for stmmac
driver to support 1588 PTP.

V2: added support for FINE method, reduced loop delay and review spinlock.
Signed-off-by: NRayagond Kokatanur <rayagond@vayavyalabs.com>
Hacked-by: NGiuseppe Cavallaro <peppe.cavallaro@st.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>