igc: remove I226 Qbv BaseTime restriction

[ Upstream commit b8897dc5 ]

Remove the Qbv BaseTime restriction for I226 so that the BaseTime can be
scheduled to the future time. A new register bit of Tx Qav Control
(Bit-7: FutScdDis) was introduced to allow I226 scheduling future time as
Qbv BaseTime and not having the Tx hang timeout issue.

Besides, according to datasheet section 7.5.2.9.3.3, FutScdDis bit has to
be configured first before the cycle time and base time.

Indeed the FutScdDis bit is only active on re-configuration, thus we have
to set the BASET_L to zero and then only set it to the desired value.

Please also note that the Qbv configuration flow is moved around based on
the Qbv programming guideline that is documented in the latest datasheet.

Co-developed-by: Tan Tee Min <tee.min.tan@linux.intel.com>
Signed-off-by: Tan Tee Min <tee.min.tan@linux.intel.com>
Signed-off-by: Muhammad Husaini Zulkifli <muhammad.husaini.zulkifli@intel.com>
Tested-by: Naama Meir <naamax.meir@linux.intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Stable-dep-of: e037a26e ("igc: Fix packet still tx after gate close by reducing i226 MAC retry buffer")
Signed-off-by: Sasha Levin <sashal@kernel.org>