net: stmmac: Add EST errors into ethtool statistic

Below EST errors are added into ethtool statistic:
1) Constant Gate Control Error (CGCE):
   The counter "mtl_est_cgce" increases everytime CGCE interrupt is
   triggered.

2) Head-of-Line Blocking due to Scheduling (HLBS):
   The counter "mtl_est_hlbs" increases everytime HLBS interrupt is
   triggered.

3) Head-of-Line Blocking due to Frame Size (HLBF):
   The counter "mtl_est_hlbf" increases everytime HLBF interrupt is
   triggered.

4) Base Time Register error (BTRE):
   The counter "mtl_est_btre" increases everytime BTRE interrupt is
   triggered but BTRL not reaches maximum value of 15.

5) Base Time Register Error Loop Count (BTRL) reaches maximum value:
   The counter "mtl_est_btrlm" increases everytime BTRE interrupt is
   triggered and BTRL value reaches maximum value of 15.

Please refer to MTL_EST_STATUS register in DesignWare Cores Ethernet
Quality-of-Service Databook for more detail explanation.

Signed-off-by: Ong Boon Leong <boon.leong.ong@intel.com>
Signed-off-by: Voon Weifeng <weifeng.voon@intel.com>
Co-developed-by: Mohammad Athari Bin Ismail <mohammad.athari.ismail@intel.com>
Signed-off-by: Mohammad Athari Bin Ismail <mohammad.athari.ismail@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>