msm: emac: Compensate the fractional ns inaccuracy

Compensate the loss of accurucy of fractional ns per clock cycle and
support the grandmaster mode.

Change-Id: I1fa073436c48c9cafe3992d39ba85b8e15467dbb
Acked-by: Jie Luo <jluo@qti.qualcomm.com>
Signed-off-by: Gilad Avidov <gavidov@codeaurora.org>