igc: Fix igc_ptp_rx_pktstamp()

stable inclusion
from stable-5.10.27
commit 5994a096570f8c90bf37a5ce4dea8904db83d0b4
bugzilla: 51493

--------------------------------

[ Upstream commit fc9e5020 ]

The comment describing the timestamps layout in the packet buffer is
wrong and the code is actually retrieving the timestamp in Timer 1
reference instead of Timer 0. This hasn't been a big issue so far
because hardware is configured to report both timestamps using Timer 0
(see IGC_SRRCTL register configuration in igc_ptp_enable_rx_timestamp()
helper). This patch fixes the comment and the code so we retrieve the
timestamp in Timer 0 reference as expected.

This patch also takes the opportunity to get rid of the hw.mac.type check
since it is not required.

Fixes: 81b05520 ("igc: Add support for RX timestamping")
Signed-off-by: Andre Guedes <andre.guedes@intel.com>
Signed-off-by: Vedang Patel <vedang.patel@intel.com>
Signed-off-by: Jithu Joseph <jithu.joseph@intel.com>
Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Tested-by: Dvora Fuxbrumer <dvorax.fuxbrumer@linux.intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Acked-by:   Weilong Chen <chenweilong@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>