igc: return an error if the mac type is unknown in igc_ptp_systim_to_hwtstamp()

stable inclusion
from stable-v5.10.168
commit 6362b861704fbf7d331bba35407927d9cd84eb9b
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7URR4

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6362b861704fbf7d331bba35407927d9cd84eb9b



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

[ Upstream commit a2df8463 ]

clang static analysis reports
drivers/net/ethernet/intel/igc/igc_ptp.c:673:3: warning: The left operand of
  '+' is a garbage value [core.UndefinedBinaryOperatorResult]
   ktime_add_ns(shhwtstamps.hwtstamp, adjust);
   ^            ~~~~~~~~~~~~~~~~~~~~

igc_ptp_systim_to_hwtstamp() silently returns without setting the hwtstamp
if the mac type is unknown.  This should be treated as an error.

Fixes: 81b05520 ("igc: Add support for RX timestamping")
Signed-off-by: Tom Rix <trix@redhat.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Acked-by: Sasha Neftin <sasha.neftin@intel.com>
Tested-by: Naama Meir <naamax.meir@linux.intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Link: https://lore.kernel.org/r/20230131215437.1528994-1-anthony.l.nguyen@intel.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: zhaoxiaoqiang11 <zhaoxiaoqiang11@jd.com>