igc: Fix TX Hang issue when QBV Gate is closed

If a user schedules a Gate Control List (GCL) to close one of
the QBV gates while also transmitting a packet to that closed gate,
TX Hang will be happen. HW would not drop any packet when the gate
is closed and keep queuing up in HW TX FIFO until the gate is re-opened.
This patch implements the solution to drop the packet for the closed
gate.

This patch will also reset the adapter to perform SW initialization
for each 1st Gate Control List (GCL) to avoid hang.
This is due to the HW design, where changing to TSN transmit mode
requires SW initialization. Intel Discrete I225/6 transmit mode
cannot be changed when in dynamic mode according to Software User
Manual Section 7.5.2.1. Subsequent Gate Control List (GCL) operations
will proceed without a reset, as they already are in TSN Mode.

Step to reproduce:

DUT:
1) Configure GCL List with certain gate close.

BASE=$(date +%s%N)
tc qdisc replace dev $IFACE parent root handle 100 taprio \
    num_tc 4 \
    map 0 1 2 3 3 3 3 3 3 3 3 3 3 3 3 3 \
    queues 1@0 1@1 1@2 1@3 \
    base-time $BASE \
    sched-entry S 0x8 500000 \
    sched-entry S 0x4 500000 \
    flags 0x2

2) Transmit the packet to closed gate. You may use udp_tai
application to transmit UDP packet to any of the closed gate.

./udp_tai -i <interface> -P 100000 -p 90 -c 1 -t <0/1> -u 30004

Fixes: ec50a9d4

 ("igc: Add support for taprio offloading")
Co-developed-by: Tan Tee Min <tee.min.tan@linux.intel.com>
Signed-off-by: Tan Tee Min <tee.min.tan@linux.intel.com>
Tested-by: Chwee Lin Choong <chwee.lin.choong@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>