stmmac: add IEEE PTPv1 and PTPv2 support.

This patch enhances the stmmac driver to support IEEE 1588-2002
PTP (Precision Time Protocol) version 1 and IEEE 1588-2008 PPT
version 2.

Precision Time Protocol(PTP),which enables precise synchronization
of clocks in measurement and control systems implemented with
technologies such as network communication,local computing,
& distributed objects.

Both PTPv1 and PTPv2 is selected at run-time using the HW capability
register.

The PTPv1 TimeStamp support can be used on chips that have the normal
descriptor structures and PTPv2 TimeStamp support can be used on chips
that have the Extended descriptors(DES4-5-6-7). All such sanity checks
are done and verified by using HW capability register.

V2: in this version the ethtool support has been included in this patch;
Koptions have been completely removed (previously added to select
PTP and PTPv2). PTPv1 and PTPv2 is now added in a single patch instead of
two patches.
get_timestamp() and get_systemtime() L/H have been combined into single APIs.

Signed-off-by: Rayagond Kokatanur <rayagond@vayavyalabs.com>
Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>