HSD #16020582471: net: stmmac: Support recalculating of CBS idle slope under EST

commit e00088735213497420f53d46c1826e8c84b7a8ec from
https://github.com/altera-opensource/linux-socfpga.git

 socfpga-6.1.55-lts.

When EST enabled, credit is accumulated only when the gate is open.
Hence, the effective data rate of the idleSlope must be increased to
reflect the duty cycle of the transmission gate associated with the
queue. The new idleSlope is calculated using the equation below:

idleSlope = (operIdleSlope(N) * OperCycle/GateOpenTime)

operIdleSlope = Calculated idle slope before EST enabled
N             = Queue number
OperCycle     = Cycle time for queue N
GateOpenTime  = Total gate open time for queue N

Signed-off-by: Voon Weifeng <weifeng.voon@intel.com>
Signed-off-by: Ong Boon Leong <boon.leong.ong@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: Michael Sit Wei Hong <michael.wei.hong.sit@intel.com>
Signed-off-by: Rohan G Thomas <rohan.g.thomas@intel.com>
Signed-off-by: Liwei Song <liwei.song@windriver.com>